KKU Res J (GS) 14 (2) : April - June 2014 1

Diversity and Distribution of Murid Rodents in Tarutao National Park – a Biogeographic Perspective ความหลากหลายและการแพร่กระจายของหนูในอุทยานแห่งชาติ ตะรุเตา – มุมมองทางชีวภูมิศาสตร์

Christopher I. Imakando (คริสโตเฟอร์ ไอ อิมมาเคนโด)1* Dr.Paul J.J. Bates (ดร.พอล เจ เจ เบทส์)** Dr.Sara Bumrungsri (ดร.สาระ บ�ำรุงศรี)*** Dr.Chutamas Satasook (ดร.จุฑามาส ศตสุข)**** ABSTRACT The species-area and species-isolation relationships as well as nestedness pattern were studied for murid rodents on five in Tarutao National Park. Live murid rodents were captured in the field using 100 live cage traps baited with either corn or banana from February – March, 2012 and in January of 2013. The traps were set in line transects. Four species of murid rodents were captured in this study – Rattus tanezumi, Maxomys surifer, Leopoldamys sabanus and Niviventer cremoriventer. Species richness was found to be highly correlated with area (r2 = 0.882) than the isolation of the Islands from the mainland (r2 = 0.474). The nestedness patterns of the murid rodents were found to be more organized than would be expected by chance. This means that the murid fauna in this National Park have been affected past by extinctions but are now well adapted to the Islands and there have been no subsequent recolonisations. บทคัดย่อ การศึกษาความสัมพันธ์ระหว่างจ�ำนวนชนิดและขนาดพื้นที่ และความสัมพันธ์ระหว่างจ�ำนวนชนิด และระยะห่างของเกาะจากแผ่นดินใหญ่รวมถึงรูปแบบ nestedness ของหนู ในบริเวณห้าเกาะของเขตอุทยาน แห่งชาติตะรุเตา ท�ำการศึกษาโดยวางกรงดักหนูในธรรมชาติโดยใช้กล้วยและข้าวโพดเป็นเหยื่อล่อจ�ำนวน 100 กรงตามเส้นส�ำรวจ ระหว่างเดือน กุมภาพันธ์ ถึง เดือนมีนาคม พศ. 2555 และ เดือนมกราคม พศ. 2556 พบหนู 4 ชนิด คือ Rattus tanezumi, Maxomys surifer, Leopoldamys sabanus และ Niviventer cremoriventer ความหลากชนิดของหนูมีความสัมพันธ์กับขนาดของเกาะ (r2 = 0.882) มากกว่าความสัมพันธ์

1 Correspondent author: [email protected] * Student, Master of Science in Ecology (International Program), Department of Biology, Faculty of Science, Prince of Songkla University, Songkhla, and Staff Development Fellow, School of Natural Resources, Copperbelt University, P.O Box 21692, Kitwe, Zambia ** Director, Harrison Institute, Bowerwood House, St. Botolph’s Road, Sevenoaks, Kent, TN13AQ, United Kingdom *** Asst. Prof. Department of Biology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand **** Assoc. Prof. Department of Biology, Faculty of Science, Prince of Songkla University, Songkhla, Thailand 2 วารสารวิจัย มข. (บศ.) 14 (2) : เม.ย. - มิ.ย. 2557

ระหว่างความหลากชนิดกับระยะห่างของเกาะจากแผ่นดินใหญ่ (r2 = 0.474) และพบว่าหนูในแต่ละเกาะ มีรูปแบบ nestedness ที่เป็นระบบมากกว่าที่จะเกิดโดยบังเอิญ ชี้ว่าสังคมหนูพื้นที่นี้ถูกก�ำหนด โดยการสูญพันธุ์ในอดีต และไม่ปรากฏการอพยพแทนที่เกิดขึ้นในเวลาต่อมา

Key Words: Species richness, Murid rodents, Tarutao National Park ค�ำส�ำคัญ : จ�ำนวนชนิด สัตว์ฟันเเทะกลุ่มหนู อุทยานเเห่งชาติตะรุเตา

Introduction from Prince of Songkhla University but The Islands in Tarutao National Park not yet published) have been basically were once part of the mainland. Although conducted in Tarutao National Park, there is no it is not known how many times that these comprehensive and exhaustive study on murid Islands have been isolated from the mainland rodents. Murid rodents are important as seed in the past, the most recent isolation is dispersers, in zoonoses and other ecological approximately 8,500 years ago (1-3). functions. Therefore the current murid rodents on these The species-area relationship is one Islands can either have originated before the of community ecology’s laws [11] and one latest separation or have dispersed to these of the most general, best documented Islands after separation from the mainland patterns in nature [12]. This is a relationship (with the mainland acting as the source in which the species richness tends to population). increase with increasing area. Since the areas According to the equilibrium model of the five Islands from Tarutao National Park of Island biogeography by MacArthur and included in this study varied in size we assessed Wilson [4] these Islands initially would have the strength of the Island area has on the unbalanced faunas, which after time relaxed species richness of murid rodents. The to equilibrium. If this is the case, then it is species-area relationship (also the species safe to assume that these Islands were formed -isolation relationship and nestedness as a result of fragmentation from a continuous pattern) is believed to be driven by immigra- mainland habitat, which supported a common tion and extinction leading to the population species pool prior to the rise in sea water reaching relaxation in distribution. levels and thus the murid rodents on these The species-isolation relationship Islands would be composed of non-random is also one of the well-studied patterns in subpopulations of the total available species nature. According to Lomolino [13] “since pool on the mainland [5]. the early 1800s, it has been well known that Whereas some studies in plants single, isolated Islands far out in the ocean [6, 7], social welfare of the local people [3], support fewer species than Islands that are a number of studies on ants [8-10], and part of a major archipelagoes or Islands that recently in bats and birds (by researchers are located nearer to continents. Therefore, KKU Res J (GS) 14 (2) : April - June 2014 3 for a variety of taxa and ecosystems, of Meijaard [18] who in his analyses excluded species richness should decline as a negative the specimens from Tarutao National Park on exponential or sigmoidal function of the basis that there was little information of isolation.” Despite having the knowledge the murid rodents from this site. that the isolation of four Islands included in The aim of this study was to apply this study are not very different we still the biogeographic theories of the species-area, tested this relationship. species-isolation and nestedness distribution Another trend that has been observed of the murid species in Tarutao National Park. in a number of insular taxa is the nestedness This will help to understand the diversity pattern. “The nested subset hypothesis was and distribution pattern of the murid formulated to describe and explain patterns rodents on the Islands in this National Park. in the community structure of insular mammals which are in the state of Materials and methods ‘relaxation’. The hypothesis states that the Study areas species comprising a less species rich fauna Tarutao National Park is located should constitute a proper subset of the in the Andaman Sea off the west coast of species in richer faunas, and that an peninsular Thailand in Province archipelago of such faunas arranged by between 6° 30´ N and 6° 44´ N latitude and species richness should present a nested 99° 44´ E and 99° 9´ E longitude [7]. It was series” [14]. This means that a less rich gazetted as a National Park in 1974, covers fauna will represent a subset of the more an area of 1,490 km2 and is described as species rich faunas and if a species is absent a coastal and marine ecosystem, IUCN in the species-rich fauna then it should also category II [19]. In 1984 Tarutao National be absent in the less species-rich fauna if was declared as an ASEAN Heritage the distribution represents a perfect nested National Park [20]. Tarutao National subsets provided they have the same source Park encompasses 51 Islands covered with populations (mostly considered to be the well-preserved virgin rainforest which have mainland or nearest major Island). a rich fauna. Most of these Islands are Suffice to say that past records considered important sites for birds [21]. of murid rodents in Tarutao National This study was conducted on five Park have exclusively been to identify the Islands in Tarutao National Park namely; murid rodents based on collections of Tarutao, Adang, Rawi, Butong and Yang museum specimens [15-17]. Therefore, little is (or Ka Ta) Islands (Figure 1). The size of these known about the biogeographic distributions Islands ranges from <1 km2 (Yang Island) of the murid rodents around the small Islands to as large as 151 km2 (Tarutao Island). The in Tarutao Nation Park and in South East various dimensions of the Islands included Asia in general. This is evident from the study in this study are summarized in Table 1. 4 วารสารวิจัย มข. (บศ.) 14 (2) : เม.ย. - มิ.ย. 2557

Trapping in the field On Adang, Rawi, Butong and Yang Live murid rodents on five Islands the traps were left at each site for at least were sampled using live cage traps baited three nights and checked once per day in early with either corn or banana from 11-16th morning and the bait was replaced/changed February and 15-20th March 2012 on Adang, at the time of checking. The traps were then Rawi, Butong and Yang Islands and from moved to new places but within the same site 5-15th January of 2013 on Tarutao Island. to cover as much microhabitat and area as At each site 25 traps were set at approximately possible meaning a total of 150 (6 days x 25 40-50m intervals (except for Tarutao Island traps) trapping nights per site. On Tarutao were the traps were spaced for approximately Island we spent three trapping nights with all 70-100m intervals considering the size of this the 100 traps at one sampling site per time. Island compared to other Islands). Further We then moved to another sampling site and at each site the traps were divided into two covered four sampling sites on this Island sets to try and maximize the area covered in total as follows; (1) on the north end we (one set had 12 traps and the other 13 traps). trapped at Phante Malacca and the places The traps were randomly set starting from near to Phante Malacca; (2) on the west side near the coast (beach) and moving towards we sampled at Ao Molae, Ao Sone and along the interior of the forest and the distance the trail leading to Ludu waterfall; (3) on the between the two sets of traps at each site eastern end we sampled at Talow Wow and ranged from 200-300 meters to try and along the trail leading to Taloh Udang; and increase the area covered. (4) our last site was at the south end and here The traps were most often baited we sampled around Taloh Udang and along with banana or corn because these are well the trail leading to Taloh Wow. This means known as the baits for trapping rats and on Tarutao Island at each site we had a total also because these were readily available in of 300 (3 days x 100 traps) trapping nights local markets. The purpose of “the baits are per station. Each point where the trap was not only to lure rats to the traps, but also to set was marked using a GPS. sustain them once they have been caught. The captured individuals were The traps were usually visited once a day in recorded, measured, sexed, and age determined, the early morning, however, where possible and then released at the same point of traps were checked twice a day to reduce the capture in the field. stress of capture [22]. The specimens were The species richness and relative identified in the field following the guide book abundance for each Island was simply by Francis [23] and the taxonomy is after established depending on the total number Musser and Carleton [24]. of individuals captured. The distribution of each species was mapped to represent the diversity of the species in the National Park. KKU Res J (GS) 14 (2) : April - June 2014 5

Results mainland. This is based on the r2 values, 0.882 Species richness for species-area relationship and 0.474 for A total of four species of murid the species-isolation relationship (Figures rodents were found in this National Park. 3 and 4 respectively). Tarutao Island which 2 Greatest species richness was found on is the largest Island (151 km ) and is the Tarutao Island (4 species), followed by Rawi closest to the mainland (26 km) had the Island (3 species), Adang Island (2 species) highest number of species and the and least on Butong and Yang Islands highest densities. The other four Islands (1 species each) (Table 2). The most are almost equidistant in terms of isolation common species was Rattus tanezumi which from the mainland (approximately was widespread across all the five Islands, 70 km from the mainland and 45 km followed by Maxomys surifer which was from Tarutao Island). Adang and Rawi recorded on three Islands (Tarutao, Adang Islands are almost equal in area (with 29.8 2 2 and Rawi) while Niviventer cremoriventer km and 28 km respectively) and were was recorded on Tarutao and Rawi Islands, found to have 2 and 3 species respectively. finally Leopoldamys sabanus was restricted However, if we include the records of to Tarutao Island only. Miller [16], who reported N. cremoriventer In terms of the abundance, a total on Adang Island but we didn’t capture in of 155 individuals of the 4 murid rodent the present survey, we can say that both species were captured. M. surifer was the Adang and Rawi Islands have three species 2 most abundant species and represented each. Butong is much smaller (4 km ) than 48.4% of the entire murid rodent individuals Adang and Rawi and had only one species. 2 captured, followed by R. tanezumi (41.3%). The smallest Island Yang (<1 km ) also has L. sabanus (7.7%) and N. cremoriventer only one species. (2.6%) were considerably less abundant. Despite the relatively small number There was no particular pattern in of Islands and rodent species included in the distribution of the species composition this study, our results showed quite a good of murid rodents captured from one site to structure in terms of distribution of the another on all the Islands (Figure 2). species on the Islands in Tarutao National Park as shown in Table 3. Our results show Effect of area and isolation on the that the distribution is thus not by chance diversity of species and their nestedness or randomly but well-structured as would pattern be predicted of a nested distribution. From Our results found that the diversity Table 3 below it can be seen that the species of species on each Island was greatly composition on each Island reflects the influenced by the area and to a lesser extent effect of area and isolation of that Island from by the isolation of that Island from the the mainland. The results show what would 6 วารสารวิจัย มข. (บศ.) 14 (2) : เม.ย. - มิ.ย. 2557 be expected of a fauna in a relaxed state or in terms of Island rodents having a tendency at equilibrium as would be predicted of a to support high densities when in suitable perfectly nested fauna. habitats according to the Island syndrome in rodents [25]. This is supported by the Discussion fact that the forest type in Tarutao National Despite the first collections of murid Park appears to be especially suitable for rodents in Tarutao National Park having M. surifer, which is reported as being a been reported during early 1900s [15-17], rain-forest dependant rat [26]. R. tanezumi the species that we found on the Islands are was the second most abundant rodent in still the same as those recorded previously. terms of the individuals captured. This is This means that the species composition over due to the fact that it was widespread across approximately a period of 100 years has been all the five Islands and is highly adaptable the same and thus we can assume that the to various habitats, including disturbed and habitats on the Islands in Tarutao National undisturbed habitats and also in human Park have not been disturbed or if they have settlements [23, 27]. Another reason could be been disturbed, it can be assumed that that R. tanezumi is a better colonizer and/ maybe murid rodents are tolerant to different or competitor than other species recorded on habitat changes. The only slight difference these Islands. R. tanezumi, being a sister between the earlier records and the current species of R. rattus [24, 28] is expected study is that we recorded N. cremoriventer to have the same behavior as R. rattus of on Tarutao and Rawi Islands while in the territorial defense; be a generalist in diet (taking previous collections this species was only almost whatever food is available); displace recorded on Tarutao and Adang Islands. smaller species such as R. exulans from This difference can be accounted for because their environmental niches; and once it the numbers of individuals of this species establishes itself to show great resilience captured were very low (with only one to natural disasters such as short time individual on Tarutao and three individuals flooding of an Island by storm surges [29]. on Rawi). Therefore, it is possible that there On the other hand, L. sabanus is is also a small population of N. cremoriventer probably restricted to Tarutao Island because on Adang but we did not capture any this is the biggest Island and only this Island individual during our study. provides enough resources and home range The results showed that M. surifer for this species. despite being found only on three out the The low density of N. cremoriventer five Islands sampled (Table 3) was the could be explained in terms of the size of this most abundant in terms of the number of animal. It is the smallest of all the species individuals captured. This would be explained recorded and is probably unable to compete KKU Res J (GS) 14 (2) : April - June 2014 7 with the larger taxa. However, it has found important to note that one exception to the a niche in forest edges which are a bit species-area relationship called the ‘small disturbed by humans and not in sympatric Island effect’ [4] was observed. The small with other species. Island effect is tendency of species richness Another point of interest was that varying independently of the Island area for despite Yang being smaller in area than smaller Islands (or biotas) [30]. This varies Butong more individuals were captured on in a manner consistent with the resource this Island than the latter despite there requirement, immigration abilities, and being more trap nights on Butong Island degree of isolation of these biotas [31]. (27 traps x 6 nights = 162 trap nights) than On the other hand the isolation of Yang Island (21 traps x 6 nights = 126 trap the Islands seemed not to have a greater nights). The higher density of R. tanezumi effect (r2 = 0.474) (Figure 4). This individuals on Yang as compared to Butong result was not surprising because with the can be explained more in terms of resource exception of Tarutao Island which had a availability and to a lesser extent in terms of different distance from the mainland, the the proximity of these two Islands to other other Islands are very close to each other small Islands. Butong as can be seen on the and hence they somewhat clumped together map (Figure 1) is located on the periphery of on the graph. It is worthy to note here that the other Islands. In addition, Butong Island this does not mean isolation of the Island has fewer fresh water sources as compared does not have an effect on the species richness to Yang Island. This latter Island, which but that the Islands included in this lies somewhat between Adang and Rawi, study were too close to each other and and has more fresh water sources and also a hence this relationship could not be rubbish pit where tourists dump their refuse, clearly assessed. Thus if someone wants including food. Therefore the food resources to test this relationship, he/she should are artificially boosting to the advantage of ensure that the Islands have varying the rodents densities on Yang Island. This distances from the mainland or the nearest may lead to increased carrying capacity big Island. and an increased reproduction rate on Yang From the pattern shown in the than Butong Island. distribution of murid rodents in this Even though we conducted the study National Park, it can reasonably be assumed on only 5 Islands, the species–area curve had that the species first colonized Tarutao Island a high r2 value (Figure 3). This indicates that from the mainland, which in turn acted the area of the Island has a great effect on as the source population for secondary the number of species on that Island. It is colonization or dispersal to the other smaller particularly striking because these Islands Islands which are further from the mainland. have a range of different sizes. It is also Another plausible explanation of the observed 8 วารสารวิจัย มข. (บศ.) 14 (2) : เม.ย. - มิ.ย. 2557 pattern could be that originally when the Conclusion Islands were still connected to each other In conclusion, it can be said that they had the same species but after isolation, despite this being the first extensive and on the small Islands there could be exhaustive research of murid rodents to competition among the species leading to be conducted in Tarutao National Park, in extinction of the less competitive. Our results terms of the number of Islands surveyed and showed a perfectly nested distribution of the number of individuals captured, more the murid rodents on the Islands in the research is required especially at the sites National Park associated with the size where we were unable to access. This would and isolation which is a characteristic of lead to a more complete list of the species extinction dominated faunas, which have richness of murid rodents in Tarutao had no subsequent recolonisations (as National Park. However, it can also be described in [32]). However it is hard to predicted in simple terms that the species confidently point out which species are lists for the Islands are not likely to change native or subsequently introduced by either much because despite sampling multiple humans or natural phenomena to the National sites in our study, as shown on the map, the Park because there is no fossil records of species composition was essentially uniform the original fauna in this National Park, within different sites on each Island. therefore, this distribution can only be associated to isolation/area of the Islands and possible extinction of the species. Acknowledgements We thank the Copperbelt Despite this being a relatively simple University (Zambia), Prince of Songkla test of the biogeographic theories discussed University (Thailand), and Harrison here, it was evident that various factors could Institute (UK) for the academic and financial be behind the current distribution patterns support. We thank the staff of the Princess of murid rodents on the Islands in Tarutao Maha Chakri Sirindhorn Natural History National Park ranging from the which faunas Museum and Natural History Museum of are actually the source populations for these Thailand for the additional specimens. species, what might be happening to the We also would like to thank the all the species post-isolation from the mainland more members in the Small Mammal and Bird than 8,500 years ago, to extinctions which Research Unit for the support. We thank the could result from human caused habitat Department of National Park, Wildlife and degradation. However, as pointed out earlier, Plant Conservation (DNP) of Thailand for because lack of supplementary information, the permission to conduct this research in it still remains unclear which mechanisms Tarutao National Park. Finally, I would like is responsible for the current species to thank my parents, Mr. and Mrs. Imakando composition on the individual Islands [33]. KKU Res J (GS) 14 (2) : April - June 2014 9 for the moral and spiritual support during 7. Congdon G. The vegetation of Tarutao this study. National Park. Natural History Bulletin of the Siam Society 1982; 30(2): 135-98. References 8. Abdullah S, Watanasit S, editors. Effects 1. Sathiamurthy E, Voris HK. Maps of of habitat on diversity of ants at th polocene sea level transgression and Tarutao National Park, Satun. 7 IMT- submerged lakes on the Sunda Shelf. GT UNINET and the 3rd International The Natural History Journal of PSU-UNS Conferences on Biosience; Chulalongkorn University 2006; 2011; Prince of Songkhla University. Supplement 2:1-43. 9. Watanasit S, Jantarit S. The ant nest of 2. Voris HK. Maps of pleistocene sea levels Crematogaster rogenhoferi (Mayr, 1879) in Southeast Asia: shorelines, river (Hymenoptera: Formicidae) at Tarutao systems and durations. Journal of National Park, , Southern Biogeography 2000; 27: 1153-67. Thailand. Songklanakarin Journal of 3. Wongbusarakum S. 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FigureFigure 1 Map 1 Map of Tarutao of Tarutao National National Park. The Park.labels T1,The T2, labels T3 and T1, T4 showT2, T3 the andsampling T4 showsites on the Tarutao sampling Island , A1 and A2 aresites the onsampling Tarutao sites Island, on Adang, A1 R1 and and A2 R2 are were the the samplingsampling sites sites on onRawi Adang, Island ,R1 B1 andwas theR2 only site sampledwere on the Butong sampling and the siteswhole onof YangRawi was Island, sampled. B1 was the only site sampled on Butong and the whole of Yang was sampled. Table 1 The Islands in Tarutao National Park included showing the length, width, highest point and area the relative distance from the mainland and the dimensions Yang estimated from Google Earth

Island Area (km2) Relative distance from mainland (km) Tarutao 151 26 Adang 29.8 ~71 Rawi 28 ~ 82 Butong 4 ~ 90 Yang 1 ~76

˂ Table 2 The number of murid rodent species captured, the total numbers of individuals and trapping effort (in terms of trap nights) on each Island during the study period.

Tarutao Adang Rawi Butong Yang # of species 4 3 3 1 1 Total # of individuals trapped 97 27 17 3 11 Total trap nights 1000 600 600 162 126

12 วารสารวิจัย มข. (บศ.) 14 (2) : เม.ย. - มิ.ย. 2557

Table 1 The Islands in Tarutao National Park included showing the length, width, highest point and area the relative distance from the mainland and the dimensions Yang estimated from Google Earth

Island Area (km2) Relative distance from mainland (km) Tarutao 151 26 Adang 29.8 ~71 Rawi 28 ~ 82 Butong 4 ~ 90 Yang <1 ~76

Table 2 The number of murid rodent species captured, the total numbers of individuals and trapping effort (in terms of trap nights) on each Island during the study period.

Tarutao Adang Rawi Butong Yang Number of species 4 3 3 1 1 Total number of individuals trapped 97 27 17 3 11 Total trap nights 1000 600 600 162 126

Figure 2 Map of species richness, relative abundance (represented by the proportions in the Figure 2 Map of piespecies chart) richness, and relative distribution. abundance The (represented colors represent by the proportions R. tanezumi in the pie(blue), chart) M.and suriferdistribution. The colo(red),rs represent N. cremoriventer R. tanezumi (blue), (green) M. surifer and (red), L. sabanusN. cremoriventer (purple). (green) and L. sabanus (purple).

Figure 3 Species-area curve of murid rodents based on the individuals captured. The graph follows the Arrhenius

equation, log10 S = c + z log10A.

Figure 2 Map of species richness, relative abundance (represented by the proportions in the pie chart) and distribution. The colors represent R. tanezumi (blue), M. surifer (red), N. cremoriventer (green) and L. sabanus (purple). KKU Res J (GS) 14 (2) : April - June 2014 13

Figure 3 Species-area curve of murid rodents based on the individuals captured. The graph Figure 3 Species-area curve of murid rodents based on the individuals captured. The graph follows the Arrhenius follows the Arrhenius equation, log10 S = c + z log10A. equation, log10 S = c + z log10A.

Figure 4 Species-isolation curve of murid rodents based on the individuals captured. Figure 4 Species-isolation curve of murid rodents based on the individuals captured. The graph follows the Arrhenius The graph follows the Arrhenius equation, log10 S = c + z log10D. equation, log10 S = c + z log10D.

Table 3 The presence-absence matrix of murid rodent species on each Island (based on all records to date). S is the total number of species recorded on each Island. Species are ordered in such a way that the most widespread is listed first and the least common last.

Species Tarutao Adang Rawi Butong Yang R. tanezumi      M. surifer    X X N. cremoriventer    X X L. sabanus  X X X X S 4 3 3 1 1

14 วารสารวิจัย มข. (บศ.) 14 (2) : เม.ย. - มิ.ย. 2557

Table 3 The presence-absence matrix of murid rodent species on each Island (based on all records to date).

Species Tarutao Adang Rawi Butong Yang R. tanezumi ✓ ✓ ✓ ✓ ✓ M. surifer ✓ ✓ ✓ X X N. cremoriventer ✓ ✓ ✓ X X L. sabanus ✓ X X X X S 4 3 3 1 1

S is the total number of species recorded on each Island. Species are ordered in such a way that the most widespread is listed first and the least common last.