Asian Gallwasp Project

The Asian Gallwasp Project: Taiwan-China Expedition 2011

 Frazer Sinclair1, Jack Hearn1, Konrad Lohse1, Chang-Ti Tang2

1. Institute of Cell, Animal and Population Biology, University of Edinburgh, Ashworth Laboratories, The King’s Buildings, West Mains Road, Edinburgh EH9 3JT, UK

2. National Chung-Hsing University, Kuo Kuang Rd. 250, Taichung 40227, Taiwan

 

Left to right - Chang-Ti Tang, Jack Hearn, Frazer Sinclair and Konrad Lohse

Introduction

The Cynipini gallwasps are a fascinating tribe of insects whose larvae induce complex and often spectacular galls on trees of the Fagaceae family. These galls support rich multi-trophic communities and are a valuable ecological model system. The majority of the ~1000 known Cynipini species are associated with trees of the genus Quercus in North America and Europe, but it is becoming increasingly apparent that there is further undescribed diversity associated with other Fagaceae genera, particularly those endemic to Eastern and Central Asia. The inclusion of these yet undiscovered species in a phylogenetic analysis could shed new light on the geographic origin of the tribe, and reveal the evolutionary processes that govern the association between gallwasps and their host plants. The ‘Asian Gallwasp Project’ was established in 2009 by postgraduate students at the University of Edinburgh to promote study of the ecology and taxonomy of Asian gallwasps and their associated communities. The first project expedition took place during spring 2011 in Taiwan and southern China, and involved researchers from the University of Edinburgh (UK), the National Chung-Hsing University (Taiwan), and the Xishuangbanna Tropical Botanic Gardens (China). The aims were to assess gallwasp diversity on Asian endemic oaks and to collect specimens for species descriptions and phylogenetic analysis. In this article, we describe the expedition and its findings, and discuss our plans for future work.

Taiwan: March 13th – 31st, 2011

The Edinburgh members of the expedition arrived in Taichung and were taken for an excellent welcome dinner with their host, Professor Man-Miao Yang from the National Chung Hsing University (NCHU). After a day to acclimatise, we embarked on an intensive fieldwork programme that covered thirteen sites between elevations of 400 and 2200 meters (see Figure 1). Invaluable assistance in the field was provided by students from Professor Yang’s research group including Shun-Wei Hou, Sheng-Feng Lin, I-Chang Liao, and Wesley Hunting. A total of 76 different gall-types were collected, 48 of which had never previously been recorded. Notable findings included 3 new gall-types from Castanopsis uraiana at Xiaowulai that were discovered by climbing into the tree canopy using rope access methods, and hundreds of a previously unknown ‘fluffy pink leaf gall’ found on Quercus sessilifolia at Erge Mountain (Figure 2). The expedition was timed to coincide with the maturation of sexual generation galls, and back in the labs at NCHU the collected galls quickly yielded an abundance of gallwasps (Figure 3), inquilines, and parasitoids. Between fieldwork, time was found to visit Sun-Moon Lake and the 921 Earthquake Museum, and to sample the delights of ‘stinky tofu’ at the Zhongxiao night market.    


Figure 1. Google Earth images of collection sites in Taiwan (left) and Southern China (right)


Figure 2. Novel 'fluffy pink leaf gall' on Quercus sessifolia (left), and female gallwasp ovipositing on young leaves (right)


Xishuangbanna, China: April 1st – 16th

After three flights and a night in Hong Kong, we arrived at the Xishuangbanna Tropical Botanic Gardens (XTBG) where we were hosted by Professor Charles Cannon. During the two week visit, galls were collected within the grounds of XTBG and at several sites within Xishuangbanna and neighbouring Lan Cang County, between 500 and 1700 meters elevation (Figure 1). Valuable field assistance and botanical expertise were provided by XTBG staff including Jing-Xin Liu and Jian-Wu Li. A total of 41 gall different gall-types were collected, 37 of which had never been recorded before. Galls were reared in Professor Cannon’s laboratory at XTBG with much appreciated assistance from PhD student Warin Harrison. Notable findings included 3 novel gall-types from a single tree of Castanopsis echinocarpa at Foufang quarry (Figure 4), all of which produced adult gallwasps within days of collection. Also at this site, there was the unique opportunity to examine a species of the rare Fagaceae genus Trigobalanus, although no evidence of gallwasps could be found. To celebrate the end of a successful expedition, we received a thorough soaking at the Dai new-year water splashing festival in Menglun.


 Figure 3. One of three novel gall types from Castanopsis echinocarpa from China


Preliminary analysis and results

Cynipini galls were sampled from tree species in each of the genera Castanopsis, Lithocarpus, and Quercus, in both Taiwan and China (Table 1). The majority of collected gall-types were novel (85/115), and their discovery represents a substantial addition to knowledge of Asian Cynipini. Analysis of the number of gall-types per individual tree species indicated that there was no significant difference in gall diversity between the three genera (ANOVA, p=0.753). This is somewhat surprising, as almost all currently described Cynipini species are associated with trees of the genus Quercus. Approximately 450 species of Quercus are known globally, which is comparable to the combined number of Castanopsis and Lithocarpus species (~120 and 300 respectively). If the true diversity of gallwasps per tree species is even remotely similar across these taxa, as these findings suggest, then Asia is likely to be home to hundreds more undescribed gallwasp species representing a considerable proportion of the tribe.


Table 1. Summary of gall-types and host tree species recorded in Taiwan and China

Country

Tree Genus

No. Gall-types

No. Tree species

Mean No. gall-types

per tree species

No. Gall-types that

produced adult gallwasps

Taiwan

Quercus

40

12

3.33

17

Castanopsis

20

6

3.33

2

Lithocarpus

15

7

2.14

0

China

Quercus

12

8

1.50

2

Castanopsis

20

7

2.86

4

Lithocarpus

10

3

3.33

0

Taiwan + China

Quercus

51

19

2.68

19

Castanopsis

39

12

3.25

6

Lithocarpus

25

11

2.27

0














The monitoring of collected galls is ongoing, and adult gallwasps have so far been obtained from 25 different gall-types (Table 1). Particularly notable are the 6 types from galls on Castanopsis (e.g. Figure 5), which more than doubles the number of species currently recognised from this tree taxon. Unfortunately no adult gallwasps have yet been obtained from Lithocarpus galls, despite 25 different gall-types having been collected. This may reflect particularly high rates of colonisation by inquilines or parasitoids that cause the death of the gall-former. Alternatively, it was noted that several gall-types had fresh exit holes, and it is possible that the collections were conducted too late in the season for galls from these trees

 Figure 4. Novel gall-type on Castanopsis sp. in China

Further work

Gall rearing continues at NCHU and XTBG and it is expected that the majority of adult wasps will have soon emerged. Specimens shall be transferred to the University of Edinburgh, where their DNA will be sequenced and combined with existing data to generate a phylogeny of the Cynipini tribe. This shall be used to assess; (1) what is the likely geographic origin of the Cynipini tribe? And (2), what are the relative roles of parallel cladogenesis (i.e. diversification in unison with host-plant) and host-shifting (i.e. switching between distinct host-plant taxa) in the evolution of the Cynipini? Following analysis of DNA sequence data, morphological analysis shall be conducted in collaboration with Dr George Melika, a world renowned expert in Cynipid taxonomy. Formal descriptions of novel species will be published in taxonomic journals, and type specimens shall be deposited in the collections of appropriate institutions in Taiwan and China.

It is evident from the findings of this expedition that a considerable proportion of the Cynipini tribe has yet to be discovered within Asia. With the collected specimens we can begin to place Asian Cynipini ithin the phylogeny of the group, but more comprehensive sampling is required, particularly for those species associated with Lithocarpus. As our collection of specimens grows so can the scope of our investigations, with the potential for further studies of the phylogeography of Cynipini in Asia, and the phylogenies of gall associated inquilines and parasitoids. It is expected that this was just the first of many successful Asian Gallwasp Project expeditions.

Acknowledgements  The expedition team are extremely grateful to have been awarded a Royal Entomological Society outreach grant of £1000, and also for the funding provided by the Davies Expedition Fund, the Weir Fund for Field Studies, the Royal Geographical Society with IBG, the Gilchrist Educational Trust, and the James Rennie Bequest.

We are also most grateful to Professor Man-Miao Yang and Professor Charles Cannon for hosting the expedition, and for the assistance of staff and students at NCHU and XTBG, particularly Miss Yi-Chuan Li and Mr Song Yu.       


* This page is adapted from an article for Antenna - the Bulletin of the Royal Entomological Society - currently in press.

Make a Free Website with Yola.