An ecological perspective on Joseph Rock’s (1884–1962) plant collection activities in China

Abstract

In the early 20th century, numerous western botanists, often referred to as ‘plant hunters’, embarked on ambitious expeditions to China, playing a crucial role in the study of botany and botanical diversity. Despite their contributions, comprehensive assessments of their explorations are lacking. To bridge this gap, this article focuses on the work of Joseph Charles Francis Rock, a notable figure in that era. Our work revisits Rock’s botanical expeditions within the broader context of botanical diversity conservation. It outlines his historical experiences in collecting plants in China and enumerates the species composition and phenotypic traits of the plants he collected. Additionally, it also analyzes the spatial distribution of the species, the completeness of his collection and the α- and β-diversity of the plants he collected. Our findings reveal that Rock led four major botanical expeditions in China between 1922 and 1933, amassing a total of 28 184 sheets and 16 608 numbers across 204 families, 1081 genera and 4231 species. His focus was predominantly on ornamental species, which exhibit a variety of flower colors and inflorescences. His collection work spanned 5 provinces, 35 cities and 72 counties, with a notable concentration in the Hengduan Mountains, a current biodiversity hotspot. This study not only reconstructs Rock’s botanical legacy but also offers valuable historical data and fresh analytical insights for understanding contemporary plant diversity. It contributes to the ongoing discourse on the importance of preserving plant diversity as a cornerstone of environmental sustainability.

摘要

约瑟夫·洛克在中国进行植物采集历程的生态学视角

在20世纪早期，许多西方植物学家，通常被称为“植物猎人”，在中国进行了广泛而深入的植物考察活动，对植物学和植物多样性方面的研究发挥了重要作用。尽管他们取得了丰厚的成果，但目前对他们在华考察的全面评估仍然不足。为此，本文重点研究了这一时期的著名人物约瑟夫·查尔斯·弗朗西斯·洛克的考察成果。本研究是在植物多样性保护的背景下，重新审视了洛克的植物采集过程。文章概述了他在中国采集植物的经历，并梳理了他所采集植物的种类组成和表型特征。此外，本文还分析了这些植物的空间分布、采集的完整性以及α和β多样性。研究结果发现，洛克在1922至1933年间在中国进行了4次主要的植物考察，共采集了28 184份标本，16 608号标本，覆盖204个科，1081个属和4231个种。他采集的植物主要为观赏植物，具有多样的花色和花序。他的采集工作遍及5个省、35个市和72个县，并且集中在当前生物多样性热点地区，即横断山脉地区。本文不仅全面研究了洛克的植物采集成果，还为当代植物多样性保护提供了宝贵的历史数据和新的见解。此外，本研究也为讨论植物多样性保护对环境可持续性的重要性提供了支持。

INTRODUCTION

In the field of plant diversity research, the collection of plant specimens is invaluable. It provides a wealth of useful information on the distribution, morphological characteristics and ecology of plant species (Lavoie 2013; Mosena et al. 2018; Murray-Smith et al. 2009; Renner and Rockinger 2016; Teixeira-Costa et al. 2023; Willis et al. 2017). This practice has a long history among western botanists (Bretschneider 1881). Due to its unique geographical and climatic conditions, China encompasses diverse vegetation types, boasting more than 35 000 species of higher plants (Li and Miao 2016; Mi et al. 2021; Yang 2015). Consequently, the ‘Golden Age’ of plant collection in China began to take shape in the early 20th century, emerging as a pivotal avenue for western exploration of Chinese plant diversity (Lemmon 1968; Luo 2005; Stoner and Hummer 2007). Notable collectors include Ernest Henry Wilson (1876–1930), George Forrest (1873–1932) and Joseph Charles Francis Rock (1884–1962) (Forrest 2010; Glover et al. 2012; Holway 2018; Stoner and Hummer 2007). Their efforts enriched the collections of botanical museums. It unveiled the rich and diverse plant world in China and provided a historical record of plant diversity data, include past morphological characteristics and so on, contributing significantly to current plant research (Gotelli et al. 2023; Heberling 2022; Rocha et al. 2014). Early scholars briefly mentioned the overall progress of Chinese botany in relation to western expeditions. They quantified the number of western individuals involved in plant collection in China and noted their respective nationalities (Chen and Zeng 1987; Coats 1969; Gong 1919; Li 1983; Yu 1946). However, there was a lack of targeted studies on specific collectors, which highlights the need for focused research on individual collectors and their contributions to the field.

In plant collection activities, the collector, as the central figure, significantly influences the quality of collection outcomes through their experiences, skills and understanding of plant diversity (Liu et al. 2023; Whitfield 2012). Research indicates that throughout history, most specimens were collected by a select few individuals (Aung et al. 2023; Bebber et al. 2012; Daru et al. 2018). Consequently, the study of collectors has become a pivotal focus in current botanical research. For example, Kang (2011) used the case of the British plant hunter Robert Fortune (1812–80) to describe the process of the British official scientific investigation abroad. Li (2015) studied museum activities during the Macartney Embassy. This understanding aids in delineating plant diversity in specific regions, thereby offering significant reference value and implications for contemporary plant diversity conservation. However, these works are primarily popular literature and lack research from the perspectives of botany or plant diversity. Even if there are, studies merely provide a simplistic listing of achievements at the genus and species levels, lacking a thorough analysis of species diversity (Liang and Qin 2023; Wu et al. 2022). Different collectors engage in collection activities with varying objectives, routes and preferences. An in-depth study of these activities is therefore beneficial for clarifying the specific actions and impacts of collectors within historical contexts.

Among numerous western botanists, the Austrian-born American plant collector Joseph Charles Francis Rock exhibits some notable characteristics. First, with the support of renowned institutions such as the United States Department of Agriculture (USDA), the National Geographic Society (NGS) and the Arnold Arboretum of Harvard University (HAA), Rock embarked on a 27-year expedition to China starting in Yunnan in 1922. During this time, he collected a substantial number of plant specimens and documented his in-depth understanding of Asian cultures through text and imagery, providing rich historical data for subsequent studies (Sutton 1974). Second, Rock’s collections were primarily concentrated in Southwest China. His focused strategy reflects his profound understanding of the region’s plant diversity. Additionally, in the later stages of his time in China, Rock developed a keen interest in the ethnic cultures of southwest China. His explorations extended beyond plant collection to in-depth studies of Naxi culture and folklore (Rock 1955). As for the research on Rock, Sutton (1974) wrote a biography based on Rock’s diaries, correspondences and other first-hand materials, summarizing his experience of visiting China from the perspective of history. Other scholars gradually shifted their focus from national culture to plant collection achievements of him (Edwards and White 1998a, 1998b; Han and Li 2013; Li 2023; Liu 2013, 2017; Michailovsky and Michaud 2006). Although numerous scholars have documented Rock’s life and botanical expeditions, their studies often overlook his contributions to plant diversity. Importantly, previous accounts indicate that, despite the limited technology and precision of his era, Rock, a skilled botanist, exhaustively collected plants within his capabilities. His methodology closely resembled best practice sampling of local flora at the time. Thus, Rock’s comprehensive and sustained collecting efforts serve as a unique historical data source for contemporary research. They offer a valuable perspective on plant diversity from a century ago, distinct from modern field surveys.

Based on previous descriptions of the characteristics of his activities, we evaluated Rock’s extensive plant collections in China from a quantitative perspective, focusing on three main areas: (i) We analyzed species statistics and characteristics of Rock’s collections, including flower color and inflorescence, revealing key groups through sheets and collection numbers. (ii) To assess the intensity and efficiency of his work, we assessed the integrity of collected plants across three taxonomic levels—family, genus and species, as well as the spatial distribution of collection intensity. (iii) We analyzed the α- and β-diversity of Rock’s collections, revealing the patterns of plant diversity and spatial variations in species composition. This study not only highlights Rock’s significant role in the history of plant collection in China but also aids in expanding the application of historical botanical data in contemporary plant diversity research.

MATERIALS AND METHODS

Sources of specimen data

To obtain specimen data, we used ‘Rock’ as the keyword when searching comprehensive online databases (Supplementary Table S1) and several online herbarium (Supplementary Table S2). To ensure the completeness of Rock’s specimen data, we consulted manuscripts housed in Harvard University’s library, including route maps, and scanned the field notes of the  Rhododendrons collected by Rock from the Royal Botanic Garden Edinburgh. By supplementing the specimen data with these text sources, we ultimately compiled 28 184 records of plant specimens collected by Rock in China.

Verification of specimen data

To validate botanical names, we used databases such as IPlant (http://www.iplant.cn/, accessed on November 2022), Species 2000 China Node (http://www.sp2000.org.cn/, accessed on November 2022) and Flora of China (http://www.efloras.org/, accessed on November 2022) and complemented this validation by cross-referencing with databases such as WFO Plant List (http://www.wfoplantlist.org/, accessed on November 2022) and Plants of the World Online (POWO, https://powo.science.kew.org/, accessed on November 2022).

To validate the collection date, we adhered to the principle of matching the same collection number with the same species and collection dates. This allowed us to supplement the specific year and month of collection time based on Rock’s documented collection experiences. We then corrected erroneous dates, such as entries whose dates did not fall within Rock’s lifetime.

To validate the collection place, we referred to ‘The Place Name of Chinese Plant Collection’ (Du et al. 2024) and used the early Chinese specimen collection locality study (CVH, https://www.cvh.ac.cn/topics/counties.php, accessed on December 2022). Then we mapped the geographical information recorded in Wade–Giles romanization in the specimen records to the present-day city or county (district) level based on current administrative divisions. Moreover, guided by the geographical details documented in Rock’s biographies, we excluded specimens with erroneous collection sites, such as places in Guangdong and Zhejiang, which were not mentioned in his records.

To standardize collection numbers, we adhered to the principle that each collection number should correspond to the same specimen information. For specimens with identical collection numbers but differing species data, we added suffix letters to the original numbers to distinguish them.

In total, we cataloged 24 851 specimens, all from the period 1922–1933, with complete taxonomic information (family, genus and species) and geographic locations pinpointed to the county level.

Data analysis

Analysis of species composition and phenotypic traits

To understand the basic situation of Rock’s plant specimen collection in China, we not only calculated the monthly totals of collected specimens and collection numbers, but also quantified these data at the family, genus and species levels.

To analyze plant phenotypic traits, we first quantified the number of specimens collected in terms of flower color and inflorescence type. Our species trait data were sourced from iplant (https://www.iplant.cn/, accessed on July 2023). We referred to the Munsell Color Order System and Botany to standardize the types of flower color and inflorescence (Billmeyer and Bencuya 1987; Cochrane 2014; Ma 2019).

Analysis of collection distribution and completeness

To illustrate the spatial pattern and intensity of Rock’s collected specimens in China, we collated collection site information at the county level and counted the number of specimens at each site.

To assess the completeness of Rock’s collections, we used the county-level records of specimen collection sites as sampling points and defined the measure of sampling effort as the number of Rock’s sampling sites. Then we used species accumulation curves to represent the functional relationship between the cumulative number of species collected by Rock and the effort expended during sampling (Baek and Park 2022; Moreno and Halffter 2000; Willott 2001).

Analysis of species diversity

α-Diversity indices measure species richness and evenness within a single ecosystem, while β-diversity indices assess differences in species composition between different ecosystems (Thukral 2017). Simpson index describes the probability that the number of individuals obtained from two consecutive samples of a community species belongs to the same species. It is commonly used to measure the dominance of certain species in a community. The Shannon–Weiner index is used to describe the disorder and uncertainty of individuals of a species. Species richness is the number of species in an area.

For the α-diversity, using counties as sampling points, we calculated α-diversity indices (Simpson, Shannon and Species richness) at the family, genus and species levels using the vegan package in R-4.3.0 (Oksanen et al. 2007; R Core Team 2023). This analysis revealed the distribution of various diversity indices and compared α-diversity among provinces. For β-diversity, we calculated dissimilarity values at the family, genus and species levels using the ‘vegdist’ function in the vegan package. We then used principal coordinates analysis to determine similarities or differences in the collection outcomes of different provinces (Oksanen et al. 2007).

RESULTS

Species composition and plant traits

According to Rock’s employment organization and the time point of his trip to and from China and the USA, we divided his plant collection process into four stages. Phase I was principally under the aegis of the USDA and NGS. Phase II under the HAA. Phase III marked a return to the NGS. Phase IV was mainly commissioned by the HAA and UCBG, but most of the collections were procured by Rock’s assistants. Fig. 1 shows the monthly collection plants (number of sheets and numbers) collected by Rock in China from 1922 to 1933. The aggregate collection volume exhibits a gradual decline over the period, with a pronounced annual cyclical pattern in collections peaking mid-year.

Our research statistics show that from 1922 to 1933, Rock collected a total of 28 184 sheets and 16 608 numbers in China. Of these, 28 181 sheets were identified at the family level, 28 143 at the genus level and 27 173 at the species level. After verification, all the plants were classified into 204 families, 1081 genera and 4231 species. Among the 28 184 sheets collected by Rock, a noteworthy total of 208 specimens have been identified as type specimens (Supplementary Table S3), representing the foundational material for the formal description of new plant species.

We present the top 20 families, genera, species with the highest number of specimens (Supplementary Figs S1 and S2). The most frequently collected families included Ericaceae (4439 sheets, 3461 numbers), Rosaceae (2523 sheets, 1537 numbers), Asteraceae (2474 sheets, 1380 numbers), Primulaceae (1971 sheets, 963 numbers) and Ranunculaceae (1534 sheets, 893 numbers). The most frequently collected genera included Rhododendron (4041 sheets, 3255 numbers), Primula (1457 sheets, 716 numbers) and Pedicularis (893 sheets, 451 numbers). The most frequently collected species included Rhododendron rex subsp. fictolacteum (122 sheets, 111 numbers), Rhododendron beesianum (116 sheets, 95 numbers) and Rhododendron phaeochrysum var. levistratum (100 sheets, 90 numbers).

For flower color, Rock collected the highest proportion of plants with white-pink flowers (30.28%), followed by red-yellow (25.08%) and blue-purple (24.46%). Plants with black-brown flowers were the least represented at 0.66% (Fig. 2a). In terms of inflorescence, most of the flowers were umbel (24.52%) or raceme inflorescences (20.61%), with only 0.18% classified as spadix inflorescences (Fig. 2b).

Collection distribution and completeness

Based on the collected plant specimen data in this study (24 849 sheets), it is evident that from 1922 to 1933, Rock’s botanical collection activities spanned 5 provinces (Yunnan: 13 937 sheets, Sichuan: 4755 sheets, Gansu: 3630 sheets, Xizang: 1393 sheets, Qinghai: 1134 sheets) (Fig. 3a), 35 cities (Fig. 3b) and 72 counties (Fig. 3c). Among them, the five cities with the highest collection numbers were Lijiang (7611 sheets), Diqing (3956 sheets), Liangshan (3501 sheets), Gannan (3212 sheets) and Garzê (1204 sheets). The five counties with the highest collection numbers are Yulong (6240 sheets), Dimuji (3503 sheets), Deqin (2008 sheets), Zhuoni (1657 sheets) and Diebu (1258 sheets).

Supplementary Fig. S3 shows the species accumulation curves of Rock’s botanical collections in China, which revealed the relationships between collection efforts and collection points across three taxonomic levels: family (a), genus (b) and species (c). At the three taxonomic levels, the saturation of each category decreases respectively. Overall, as the number of sampling sites increases, the quantity of new records at the family, genus and species levels initially rises rapidly and then increases more slowly. From this, it can be inferred that if sampling sites continue to increase, the likelihood of Rock collecting new species approaches zero. This confirms the sufficiency of Rock’s collection activities. Moreover, as the number of sampling points increased, the confidence intervals narrowed, suggesting more precise estimates of species diversity with increased collection efforts.

Species diversity

Simpson index (reflecting the degree of community aggregation) is mostly concentrated around 0.9 (Fig. 4a–c). This indicates that a single species played a leading role in many points collected by Rock a hundred years ago, suggesting that the species distribution was not so uniform. These points were mostly found in Yunnan, Gansu and Qinghai provinces (Fig. 5a–c). The Shannon index is mostly clustered around 0 (Fig. 4d–f), which also indicates that the plant diversity in the Rock collection site was not very high 100 years ago, especially in Yunnan Province and Sichuan Province (Fig. 5d–f). Similarly, species richness mostly clustered around 0 (Fig. 4g–i). This indicates that the number of species in many sites collected by Rock a hundred years ago was not very large. Only a few sites in Yunnan and Sichuan showed high plant diversity (Fig. 5g–i).

According to the results (Fig. 6), there are slight differences in the results collected at the family and species level in Yunnan. However, in general, there was a large amount of overlap in the collection results of the five provinces, i.e. the composition of Rock’s plant collection results in different provinces was similar, indicating that Rock’s collection activities were less different between provinces.

DISCUSSION

Composition and traits of Rock’s plant collection

The plants collected by Rock revealed a focus on ornamental species. Nearly half of his specimens belonged to families renowned for their horticultural appeal, such as Ericaceae, Rosaceae, Asteraceae and Primulaceae. This trend likely stemmed from the aesthetic and commercial value highly regarded in the West during the early 20th century. During this period, horticultural societies and commercial nurseries eagerly sought new plants to enrich their gardens (Luo 2000). After realizing that western China was a haven for wildflowers, notable flower seed companies dispatched collectors such as Forrest and Francis Kingdon-Ward (1885–1958) to gather Rhododendrons and other flowers (Luo 1994, 2005). This initiative left a direct legacy for the botanical diversification of western gardens and landscapes. Although Rock arrived in Yunnan for plant collection after them, his extensive study and documentation of known species enriched botanical data, particularly for Rhododendron and Primula. This work highlighted the western researchers’ keen interest in the unique diversity of Chinese plants. Rock’s comprehensive collection of these genera aided in the West’s perception of China as the ‘mother of gardens’ and underscored the region’s status as a plant diversity reservoir. This study observes that the peak in plant collection volumes during the mid-year likely reflects the seasonal behavior of collectors, a finding i.e. also echoed in the research by Panchen et al. (2019). From the collectors’ perspective, summer usually offers extended daylight hours and warmer weather conditions, enabling more prolonged field activities. From the perspective of plant growth, summer is a period of vigorous growth for most plants. During this time, phenotypic characteristics such as flowers, leaves and fruits are most prominent. Collectors often utilize this opportunity for large-scale collections to ensure the acquisition of specimens that are representative and valuable for research.

Type specimens are the cornerstone of taxonomic nomenclature, serving as the definitive reference for the identification and classification of new species. The identification of such a significant number of type specimens in Rock’s collections not only highlights the diversity and richness in southwest China, but also emphasizes the critical role of Rock’s meticulous specimen collection in uncovering new species. The incorporation of these types of specimens into the scientific corpus not only enriches the global taxonomic databases, but also provides an invaluable reference point for future studies on plant evolution and ecology.

Plants with white-pink flower colors are more prevalent in Rock’s collection, while those with yellow-red and blue-purple flower colors also have a significant representation. This indicates Rock’s strong interest in plants with different flower colors. Plants with umbel and raceme inflorescence types are common in Rock’s collection, possibly because these two inflorescence types are widespread in plants or because Rock finds them easier to identify and collect (Benlloch et al. 2007; Stebbins 1973). This not only reflects Rock’s personal interests, but also the horticultural need before the mid-20th century. The issue of collection biases has been extensively explored in past research, revealing that collectors may be influenced by various factors when selecting plant samples, such as morphological characteristics, distance from main roads or traditional uses (Adamo et al. 2021; Batke et al. 2022; Meyer et al. 2016; Schmidt-Lebuhn et al. 2013). These factors may lead collectors to preferentially choose certain species when collecting plant samples, impacting the accuracy and reliability of the research results. Therefore, during the collection process, collectors should take measures to minimize this bias to ensure the objectivity and scientific nature of research data.

Rock’s collection hotspots coincide with contemporary biodiversity hotspots

We found that there is a clear geographical concentration in Rock’s plant collection, especially in the Hengduan Mountains region (HDM), which is one of the hotspots of global biodiversity. It is worth noting that, although Rock also ventured to collect specimens in the Anyemaqen Mountains and Qilian Mountains, the collection results from this area appear relatively less abundant than those from the HDM. This indicates that HDM has become one of the regions with notable species richness and endemism a century ago (Sun et al. 2017). This provides modern scientists with a baseline of historical data to trace past species distribution and composition, contributing valuable insights for understanding and conserving current global biodiversity hotspots.

The HDM in Southwest China is in a global biodiversity hotspot. This region serves as both an origin and refuge for alpine plants and exhibits a variety of ecological characteristics (Ding et al. 2020; Sun et al. 2017). Its rich vertical geographic gradients, diverse climate types and various habitats such as mountains, canyons and plateaus create unique conditions for the region’s plant diversity (Liang et al. 2018; Xing and Ree 2017; Yao et al. 2010; Yin et al. 2020). In contrast, Anyemaqen Mountain, located in the Nagqu region, has relatively uniform topography and harsh habitat conditions. It lacks the geographical and climatic diversity of the HDM, thereby limiting its plant species diversity (Chingii 1926). According to Yu et al. (2020), the HDM has 184 families, 1273 genera and 8439 seed plant species. In contrast, there are only 56 families, 251 genera and 752 species of seed plants in Anyemaqen Mountain (Wu 2004). This difference might result in a relatively limited collection of plant specimens by Rock in Anyemaqen and other mountains. In addition, the climatic conditions faced by Rock’s original collection activities may also be one of the reasons for this collection situation. ‘The high latitude, the high altitude, and the cold winds blowing from the Inner Mongolia desert made camping outside too cold for my body’, Rock wrote in his letter (Sutton 1974). ‘There (Anyemaqen) are no forests or shrubs or any kind. The only trees observed and that only in valley of the Yellow River are one species of Picea and one of a Juniper’ (Yang 2021). This remains valuable for understanding the biogeographic and ecological history of the entire region.

Species diversity of Rock’s plant collection

Through the analysis of Rock’s collection of plant specimens, we found that his collection results were relatively comprehensive under the conditions at that time. His work covered different taxa, providing a more comprehensive understanding of partial plant diversity in China. When the completeness was separately compared at the family, genus and species levels, it became evident that the collections were most comprehensive at the family level, followed by the genus and species levels. This pattern may be attributed to the fact that the family represents a higher taxonomic rank than species and genera, with species being the most fundamental unit and having the highest number by far (Gupta and Shukla 2012). In addition, β-diversity analysis showed that the composition of Rock’s plant collection results in the different provinces was similar indicating that his collection activities varied little between provinces. This conclusion can be inferred that in the historical period of various conditions a hundred years ago, Rock, as an experienced professional plant gatherer, kept his collection strategy relatively consistent at different collection sites and did not show prominent changes.

The Simpson and Shannon indices are metrics used to assess biodiversity, encompassing both species richness and evenness (Thukral 2017). Our analysis of the species diversity in Rock’s collections reveals that species distribution across most of his collection areas was uneven, with particularly low species richness noted within specific collection sites, especially in Yunnan Province. This indirectly reflects the state of plant diversity during that period, which contrasts with modern studies that identify Yunnan as a region rich in plant diversity (Huang et al. 2016; Qian et al. 2020). Excluding the possibility that Rock might have biased his collections toward a few species he was familiar with, another possibility is that plant diversity has indeed changed over the past century (Pereira et al. 2012). This suggests that future research could use these historical data to depict the baseline state of past plant diversity more accurately. This, in turn, can help assess the impact of human activities and natural environmental changes on biological communities.

Rock’s plant collection activities’ implications for global plant diversity conservation

Biodiversity plays a crucial role in supporting human survival, and plant diversity is the foundation of biodiversity and the basic guarantee for national and global ecological security. Western countries recognized this early, which promoted the large-scale collection of plants in western countries during the 19th and 20th centuries to enrich plant species and cultivate new plant varieties. Using 1840 and 1900 as markers, the history of western biological collection in China is divided into three phases: early, middle and late (Luo 2005). Rock’s collection activities, which began in 1922, fall into the last phase, characterized by more in-depth and comprehensive western biological exploration. His extensive collections played a key role in enhancing the western understanding of the plant diversity of Southwest China, particularly advancing the development of the USDA and Arnold Arboretum (Li 2013). Particularly, Rock’s introduction of peony seeds from China to the West not only facilitated extensive scientific studies but also significantly enhanced global recognition of China’s biodiversity (McLewin and Chen 2006). Rock’s contributions go beyond what comes from its role as a plant gatherer. The naming of these plants after him not only honors his contributions but also underscores the crucial role those early explorers played in bridging eastern and western botanical sciences. Compared with other collectors, Rock’s distinctive feature is the parallel conduct of ethnographic research alongside his botanical collections in China. This approach meant that the species he collected also reflected aspects of the local culture. For instance, Rock documented how Tibetan herders brewed tea with fig trees while driving yaks and used branches of Juniperus in their tent stoves during rituals to honor mountain gods (Wagner 1992). These observations not only highlight local plant usage practices but also reveal the cultural and religious significance of these plants, thereby enriching our understanding of the region’s plant diversity.

The large-scale plant collection activities of western countries did enrich the plant diversity, but it was unfair practice. At present, the international community has formed international laws related to the protection of plant genetic resources. These laws aim to properly protect and effectively utilize plant genetic resources worldwide and to facilitate relevant collaborative efforts. Countries around the world should strictly abide by the Convention on Biological Diversity (CBD) and vigorously promote the protection of plant diversity, so that the plant resources of all countries can be protected, restored and developed (Wu et al. 2022; Xue 2021; Yu et al. 2021). While maintaining the balance of the ecological environment, government functional departments strengthen the protection and utilization of plant genetic diversity and species diversity. Additionally, they should enhance public awareness of plant intellectual property rights and ecological environment protection.

CONCLUSIONS

Rock’s plant collection activities in China have provided profound insights into the region’s rich plant diversity. His work encompassed a wide range of plant groups, with a particular emphasis on the collection of ornamental species. A comprehensive analysis of Rock’s records revealed plant diversity hotspots in Southwest China. This provided key details on species types, indicator species, distributions and species richness and evenness, which are essential for understanding the region’s ecological information. Moreover, Rock’s contributions to botanical history demonstrate that meticulous collection and documentation not only had a significant impact on scientific research at the time but also continued to play a crucial role in contemporary studies and conservation efforts related to plant diversity.

With the continuous development of online biological databases, obtaining historical specimen data has become more convenient and efficient. Despite extensive efforts to aggregate specimen data from global databases and herbaria, challenges persist due to gaps in digitization, record inconsistencies and access restrictions (Qian et al. 2018; Yang et al. 2013). These challenges highlight the urgent need for further development of online databases. Although this study has endeavored to collect all of Rock’s plant specimens from various sources as comprehensively as possible, we acknowledge that it is impossible to estimate all species that he encountered in the field. In the process of organizing the specimen data, we have identified cases of incomplete information, such as missing key details like geographic coordinates and elevation. This serves as a caution to contemporary plant specimen collectors about the importance of thorough and accurate data recording. This also urges them to enhance information completeness during the collection process, achieve effective and objective sample collection and provide more possibilities for subsequent research (Sullivan and Nazaire 2022). The results of Rock’s specimen collection in China contribute to the identification of type specimens. This not only highlights the indispensable role of traditional taxonomic practices in contemporary plant diversity research but also underscores how comprehensive field investigations and meticulous specimen documentation are linked to sustainable development goals. Consequently, the contemporary scientific community must continue to support and carry out detailed specimen collection work. Above all, research on historical plant specimen data should not be limited to reframing the historical plant collection experience. Instead, it should leverage new statistical knowledge to delve into the potential value within, offering insights for contemporary plant diversity (Watanabe 2019).

The plant specimen data collected by numerous renowned Western collectors like Rock in China present a significant research opportunity. These historical datasets not only provide us with a rich repository of biodiversity information, but more importantly, they offer a unique historical perspective on modern ecological studies in the context of rapid global biodiversity changes (Rocchetti et al. 2021). Future research like climate adaptation strategies and ecological restoration should focus on unlocking the potential value of these underexplored data. This could involve reevaluating the data with more precise analytical methods or comparing them with contemporary data to reveal trends in biodiversity changes over the past century.

Supplementary Material

Supplementary material is available at Journal of Plant Ecology online.

Figure S1: Top 20 families (a), genera (b) and species (c) with the highest number of sheets in Rock’s plant collection in China.

Figure S2: Top 20 families (a), genera (b) and species (c) with the highest number of collection numbers in Rock’s China plant collection.

Figure S3: Species accumulation curves of plant specimens collected by Rock in China at the family (a), genus (b) and species (c) levels.

Table S1: Primary comprehensive database for Rock’s collection of plant specimens in China.

Table S2: Herbaria housing Rock’s collection of plant specimens in China.

Table S3: Type species collected by Rock in China from 1922 to 1933.

Authors’ Contributions

Jifan Luo (Data collection, Visualization, Methodology, Writing—original draft), Ruozhi Huang (Writing—review & editing), Hai Yan (Supervision, Writing—review & editing), Renwu Wu (Data collection, Funding acquisition, Writing—review & editing), Shuai Liao (Writing—review & editing), Zhoubing Xiang (Writing—review & editing), Yongxi Zou (Writing—review & editing), Liangchen Shi (Writing—review & editing), Ke Wang (Writing—review & editing), and Zhiyi Bao (Writing—review & editing)

Acknowledgements

We gratefully acknowledge the data supports by the National Specimen Information Infrastructure (NSII), Harvard University and the Royal Botanic Garden Edinburgh (RBGE). We thank Wenhao Hu for valuable comments on previous drafts.

Conflict of interest statement. The authors declare that they have no conflict of interest.

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