Insular Isolation Research Articles

Depauperate Small Mammal Assemblage in Wolin National Park (Poland): Effects of Insular Isolation, Topography, and Vegetation

Terrestrial small mammal species typically assemble according to plant communities, but multiple factors, including large-scale geographic patterns, influence their assemblage structure. Despite their ecological significance, small mammals are often underrepresented in biodiversity assessments, and many Polish national parks lack comprehensive surveys. This is also the case for Wolin National Park (WNP), Poland’s only national park on a coastal marine island, which is known for its unique bat fauna. Here, we surveyed small mammals in WNP using live and pitfall trapping, identifying only nine species—the lowest richness among the five regional national parks (which host 11–13 species based on trapping data alone). Rarefaction analysis indicated a very low probability of detecting additional species with further sampling. This unexpectedly low richness is likely linked to insular isolation and the park’s location at the edge of the regional distributions of three species. Cluster analysis revealed a key pattern in WNP’s small mammal assemblages: a division between two distinct landscape units—moraine hills and the alluvial delta—where Apodemus flavicollis and Apodemus agrarius were the predominant species, respectively. This division had a greater influence on assemblage clustering than local vegetation.

A new species of Hylarana Tschudi, 1838 (Amphibia: Anura: Ranidae) from the Nicobar Islands, India

A new species of Hylarana Tschudi, 1838 (Amphibia: Anura: Ranidae) from the Nicobar Islands, India

A Craniometric Analysis of the Subfamily Cervinae (Cervidae, Mammalia)

This study employs Principal Component Analysis to examine cranial measurements from both extant and fossil specimens spanning 38 species and comprising over 300 individuals within the subfamily Cervinae. Our findings elucidate craniometric distinctions among cervids characterized by varying body sizes and certain evolutionary adaptations. While our results generally corroborate previous assertions regarding the limited craniometric variability among plesiometacarpal deer, they also unveil specific cranial adaptations within certain genera and species. The Principal Component Analysis of craniometric data revealed that giant and large-sized deer display significantly broader ecomorphological diversity in cranial shape compared to small-sized deer. Secondly, small-sized deer exhibit greater uniformity in their cranial shape, appearing densely clustered on the factorial map. Thus, we conclude that body size imposes ecological constraints, limiting the available niches due to eco-physiological factors. This study demonstrates that endemic insular deer do not evolve consistent craniometric features attributable to insular isolation, while the cranial proportions of medium-to-small-sized deer delineate a ubiquitous morphological archetype characteristic of numerous cervid taxa spanning diverse phylogenetic lineages and sharing comparable body sizes. This group of “Dama-like” deer, characterized by similar body size, metabolic rates, ecological needs, and cranial morphometry, is referred to here as the fundamental eco-physiological type, typical of warm regions within the Palearctic and Oriental biogeographic realms.

Pilot Investigation of SARS-CoV-2 Variants in the Island of Sicily Prior to and in the Second Wave of the COVID-19 Pandemic.

After 2 years of the COVID-19 pandemic, we continue to face vital challenges stemming from SARS-CoV-2 variation, causing changes in disease transmission and severity, viral adaptation to animal hosts, and antibody/vaccine evasion. Since the monitoring, characterization, and cataloging of viral variants are important and the existing information on this was scant for Sicily, this pilot study explored viral variants circulation on this island before and in the growth phase of the second wave of COVID-19 (September and October 2020), and in the downslope of that wave (early December 2020) through sequence analysis of 54 SARS-CoV-2-positive samples. The samples were nasopharyngeal swabs collected from Sicilian residents by a state-run one-health surveillance laboratory in Palermo. Variant characterization was based on RT-PCR amplification and sequencing of four regions of the viral genome. The B.1.177 variant was the most prevalent one, strongly predominating before the second wave and also as the wave downsized, although its relative prevalence decreased as other viral variants, particularly B.1.160, contributed to virus circulation. The occurrence of the B.1.160 variant may have been driven by the spread of that variant in continental Europe and by the relaxation of travel restrictions in the summer of 2020. No novel variants were identified. As sequencing of the entire viral genome in Sicily for the period covered here was restricted to seven deposited viral genome sequences, our results shed some light on SARS-CoV-2 variant circulation during that wave in this insular region of Italy which combines its partial insular isolation with being a major entry point for the African immigration.

A derived dryolestid mammal indicates possible insular endemism in the Late Jurassic of Germany

The Langenberg Quarry near Bad Harzburg has yielded the first Jurassic stem therian mammal of Germany, recovered from Kimmeridgian (Late Jurassic) near shore deposits of a palaeo-island within the Lower Saxony Basin of the European archipelago. The new stem therian is represented by one lower and three upper molars. Hercynodon germanicus gen. et sp. nov. is attributed to the Dryolestidae, a group of pretribosphenic crown mammals that was common in western Laurasia from the Middle Jurassic to the Early Cretaceous. The new taxon is characterised by small size, a reduced cusp pattern in the upper molars lacking a metacone, and enhancement of the shearing crests paracrista and metacrista. Phylogenetic analysis identified Hercynodon gen. nov. as sister taxon of Crusafontia from the Lower Cretaceous (Barremian) of Spain. Both taxa belong to an endemic European clade of dryolestids, including also Achyrodon and Phascolestes from the earliest Cretaceous (Berriasian) of England. Despite its greater geological age, Hercynodon gen. nov. is the most derived representative of that clade, indicated by the complete reduction of the metacone. The discrepancy between derived morphology and geological age may be explained by an increased rate of character evolution in insular isolation. Other insular phenomena have earlier been observed in vertebrates from the Langenberg Quarry, such as dwarfism in the small sauropod Europasaurus, and possible gigantism in the morganucodontan mammaliaform Storchodon and the pinheirodontid multituberculate mammal Teutonodon which grew unusually large.

Evolutionary effects of geographic and climatic isolation between Rhododendron tsusiophyllum populations on the Izu Islands and mainland Honshu of Japan.

Geographic and environmental isolations of islands and the mainland offer excellent opportunity to investigate colonization and survival dynamics of island populations. We inferred and compared evolutionary processes and the demographic history of Rhododendron tsusiophyllum, in the Izu Islands and the much larger island Honshu, treated here as the mainland, using thousands of nuclear SNPs obtained by ddRAD-seq from eight populations of R. tsusiophyllum and three populations of R. tschonoskii as an outgroup. Phylogenetic relationships and their habitats suggest that R. tsusiophyllum had evolved and migrated from cold north to warm south regions. We detected clear genetic divergence among populations in three regions of Honshu and the Izu Islands, suggesting restricted migration between them due to isolated habitats on mountains even in the mainland. The three regions have different changes in effective population size, especially, genetic diversity and population size of the Izu Islands are small compared to the others. Further, habitats of populations in the Izu Islands are warmer than those in Honshu, suggesting that they have undergone adaptive evolution. Our study provides evidences of montane rather than insular isolation on genetic divergence, survival of populations and significance of adaptive evolution for island populations with small population size and low genetic diversity, despite close proximity to mainland populations.

Morphometrics and genetics highlight the complex history of Eastern Mediterranean spiny mice

AbstractSpiny mice of the Acomys cahirinus group display a complex geographical structure in the Eastern Mediterranean area, as shown by previous genetic and chromosomal studies. To better elucidate the evolutionary relationships between insular populations from Crete and Cyprus and continental populations from North Africa and Cilicia in Turkey, genetic and morphometric variations were investigated, based on mitochondrial D-loop sequences, and the size and shape of the first upper molar. The Cypriot and the Cilician populations show idiosyncratic divergence in molar size and shape, while Cretan populations present a geographical structure with at least three differentiated subpopulations, as shown by congruent distributions of haplogroups, Robertsonian fusions and morphometric variation. A complex history of multiple introductions is probably responsible for this structure, and insular isolation coupled with habitat shift should have further promoted a pronounced and rapid morphological evolution in molar size and shape on Crete and Cyprus.

Determining the underlying structure of insular isolation measures

AbstractAimIsland isolation is measured in many ways. We seek to determine what the underlying latent factors characterizing these measures are, in order to understand how they mechanistically drive island biogeographical patterns and in order to recommend the most parsimonious measures. We then test the discriminatory power of the identified components against hypotheses generated from the biogeographical patterns of invasive rats.LocationThe 890 offshore islands (≥1 hectare area) of the New Zealand archipelago (latitude: 34.1–47.3°S, longitude: 166.2–178.4°E).TaxonMammals.MethodsWe identified 16 measures that have been frequently used to characterize isolation in the past, including Euclidean‐based distance metrics, landscape connectivity metrics derived from least‐cost and circuit theory modelling, landscape buffers, stepping stones and insular area. We used principal components analysis (PCA) to synthesize the underlying structure of insular isolation with respect to terrestrial mammal dispersal. Finally, we tested the discriminatory power of retained principal components (PCs) using permutational multivariate analyses of variance (PERMANOVA). Tests include comparison of historical rat distributions, islands targeted for rat eradication and islands reinvaded by rats.ResultsThe underlying structure of island isolation as characterized in the 16 metrics was described by three independent PCA components. Variable clustering suggests that PC1 captured distance from the mainland source to the focal island (PC1 Distance), PC2 described stepping stones available along the dispersal pathway (PC2 Stepping Stones) and PC3 described the focal island's position in the landscape (PC3 Insular Network). Each discriminatory test affirmed its respective biogeographical pattern hypothesis.Main conclusionsThe three underlying components we identify form the basis of a robust description of insular isolation that is of broad importance to understanding island biogeography dynamics. Moreover, these components can be applied across taxa without extensive structural or functional assumptions because the highest loading variables are not biologically informed.

Understanding the Indian mainland–island biogeography through plant dispersal mechanism

The plant–disperser relationship and its key predictors in Indian tropical archipelagos are understudied. East of the Indian mainland (the Eastern coast, EC) are the Andaman and Nicobar Islands (AN, about 1221 km away at the shortest distance), which exhibit a great plant diversity, with 848 unique species. West of the Indian mainland (the Western Ghats, WG) are another group of islands, the Lakshadweep Islands (LD, about 320 km away at the shortest distance), which exhibit less diversity (102 unique species) than do the AN. We compared these two mainland–island pairs (EC–AN, WG–LD), which exhibit different insular isolation conditions, to understand the plant dispersal mechanisms and their determining predictors (plant richness, geographic area, perimeter, elevation, and shortest distance). We found epizoochory (adherence to an animal surface), ornithochory (birds), and hydrochory (water) to be the dominant dispersers of both the pairs. Additionally, the plant dispersal in the WG–LD pair is predominantly driven by anemochory (wind), possibly denoting the effects of the northeasterly trade winds. The major role of biotic dispersers in the EC–AN pair may be explained as resulting from plant dispersal to more remote islands through biotic dispersers being more rapid and efficient. The plant commonality was found to be positively correlated with the plant richness, geographic area, and perimeter; whereas it was negatively correlated with the shortest distance and elevation of the selected mainland–island pairs. Both linear (R2 = 0.85) and non-linear (R2 = 0.95) regression with maximum accuracy found island plant richness, geographic area, and shortest distance to the nearest mainland pool to be the determinants in explaining plant-dispersal mechanisms. These predictors are important to maintain the habitat suitability and connectivity and thereby support more newly dispersed plants. The plant–disperser relationship (epizoochory, ornithochory, anemochory, and hydrochory) and the key predictors (plant richness, geographic area, and shortest distance) found in this study could be useful for conservation, planning, and monitoring of biodiversity.

On the molecular and morphological evolution of continental and insular Cryptorchestia species, with an additional description of C.garbinii (Talitridae).

Semi-terrestrial talitrid amphipods of the genus Cryptorchestia (sensu Lowry and Fanini 2013) associated with freshwater-soaked leaf litter were known to occur in inland lakes of Turkey and at the shores of the Black Sea. Before 2013 they had been reported as Orchestiacavimana and later as Cryptorchestiacavimana. In our phylogenetic tree, inferred from a mitochondrial and nuclear gene dataset (cytochrome oxidase I (COI), and histone H3 (H3), respectively), we show that these Turkish populations belong to Cryptochestiagarbinii, a common and widespread continental species, which is closely related to C.cavimana (endemic to Cyprus) and C.ruffoi (endemic to Rhodes). For the Turkish and European populations of C.garbinii, we found low levels of both genetic differentiation and morphological variation, and an age-related size variability (increasing at each moult) of the small lobe in the male gnathopod I merus, the main taxonomically diagnostic character for Cryptorchestia. A mainland (C.garbinii) versus insular isolation and in situ speciation (C.cavimana, and C.ruffoi) in the two east Mediterranean islands of Cyprus and Rhodes is discussed in relation to terrestrial Cryptorchestia species endemic to North East Atlantic volcanic islands (Azores, Canary Islands, and Madeira). The incorporation of five Mediterranean and Atlantic Orchestia species in the Bayesian analysis of the two genes (COI, and H3) indicated that both genera Orchestia and Cryptorchestia are not monophyletic.

Natural history of the narrow endemics Ipomoea cavalcantei and I. marabaensis from Amazon Canga savannahs

Amazon comprises a vast variety of ecosystems, including savannah-like Canga barrens that evolved on iron-lateritic rock plateaus of the Carajás Mountain range. Individual Cangas are enclosed by the rain forest, indicating insular isolation that enables speciation and plant community differentiation. To establish a framework for the research on natural history and conservation management of endemic Canga species, seven chloroplast DNA loci and an ITS2 nuclear DNA locus were used to study natural molecular variation of the red flowered Ipomoea cavalcantei and the lilac flowered I. marabaensis. Partitioning of the nuclear and chloroplast gene alleles strongly suggested that the species share the most recent common ancestor, pointing a new independent event of the red flower origin in the genus. Chloroplast gene allele analysis showed strong genetic differentiation between Canga populations, implying a limited role of seed dispersal in exchange of individuals between Cangas. Closed haplotype network topology indicated a requirement for the paternal inheritance in generation of cytoplasmic genetic variation. Tenfold higher nucleotide diversity in the nuclear ITS2 sequences distinguished I. cavalcantei from I. marabaensis, implying a different pace of evolutionary changes. Thus, Canga ecosystems offer powerful venues for the study of speciation, multitrait adaptation and the origins of genetic variation.

Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: implications for reintroductions

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 28:117-122 (2015) - DOI: https://doi.org/10.3354/esr00681 NOTE Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: implications for reintroductions Michelle H. Reynolds1,*, John M. Pearce2, Philip Lavretsky3, Pedro P. Seixas4, Karen N. Courtot1 1US Geological Survey, Pacific Island Ecosystems Research Center, PO Box 44, Hawai‘i National Park, Hawai‘i 96718, USA 2US Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, Alaska 99508, USA 3Wright State University, 3640 Colonel Glenn Hwy, Dayton, Ohio 45435, USA 4Centro de Reprodução Anatideos, Rua Mário Pais da Costa, no. 53, 3515-174 Viseu, Portugal *Corresponding author: mreynolds@usgs.gov ABSTRACT: Conservation of genetic biodiversity in endangered wildlife populations is an important challenge to address since the loss of alleles and genetic drift may influence future adaptability. Reintroduction aims to re-establish species to restored or protected ecosystems; however, moving a subset of individuals may result in loss of gene variants during the management-induced bottleneck (i.e. translocation). The endangered Laysan teal Anas laysanensis was once widespread across the Hawaiian archipelago, but became isolated on Laysan Island (415 ha) from the mid-1800s until 2004 when a translocation to Midway Atoll (596 ha) was undertaken to reduce extinction risks. We compared genetic diversity and quantified variation at microsatellite loci sampled from 230 individuals from the wild populations at Laysan (1999 to 2009) and Midway (2007 to 2010; n = 133 Laysan, n = 96 Midway birds). We identified polymorphic markers by screening nuclear microsatellites (N = 83). Low nuclear variation was detected, consistent with the species’ insular isolation and historical bottleneck. Six of 83 microsatellites were polymorphic. We found limited but similar estimates of allelic richness (2.58 alleles per locus) and heterozygosity within populations. However, 2 rare alleles found in the Laysan source population were not present in Midway’s reintroduced population, and a unique allele was discovered in an individual on Midway. Differentiation between island populations was low (FST = 0.6%), but statistically significant. Our results indicate that genetic drift had little effect on offspring generations 3 to 6 yr post-release and demonstrate the utility of using known founder events to help quantify genetic capture during translocations and to inform management decisions. KEY WORDS: Anas laysanensis · Island endemic · Genetic diversity · Laysan duck · Reintroduction biology Full text in pdf format PreviousNextCite this article as: Reynolds MH, Pearce JM, Lavretsky P, Seixas PP, Courtot KN (2015) Microsatellite variation and rare alleles in a bottlenecked Hawaiian Islands endemic: implications for reintroductions. Endang Species Res 28:117-122. https://doi.org/10.3354/esr00681 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 28, No. 2. Online publication date: July 14, 2015 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2015 Inter-Research.

Influência biogeográfica na morfologia de diásporos

Island Biogeography focuses on island species considering evolutionary aspects subject to patterns of isolation, rates of immigration and extinction, environmental standards, such as soil, predation rate and colonization. This work aims to compare morphologically diaspores of Guapira pernambucensis (Casar.) Lund., Schinus terebinthifolius Rad. and Canavalia rosea (Sw.) DC., occurring on the island and the mainland of Environmental Protection Area of Setiba, Guarapari, Espírito Santo State. The diaspores were collected, measured and weighed in order to verify possible variations due to their insular isolation It was found that the size of the diaspores of Guapira pernambucensis (Casar.) Lund. and Schinus terebinthifolius Rad. occurring on the island are larger than the continental diaspores. To explain this variation two possibilities were raised, the first is that individuals accompanied the insular evolutionary trend, and second, the variation was caused by ecological reasons in the insular environment. Canavalia rosea (Sw.) DC., on the other hand, presented larger diaspores in the continental environment. To explain this variation two other possibilities were raised, the first is that perhaps the species have not inhabit the island long enough so that insular evolutionary trend would be accompanied; or the soil variation on the insular environment was also caused by ecological reasons.

Patterns of lizard species richness within National Parks and Biosphere Reserves across North America's deserts

Patterns of lizard species richness within National Parks and Biosphere Reserves across North America's deserts

Evolving between land and water: key questions on the emergence and history of the Hippopotamidae (Hippopotamoidea, Cetancodonta, Cetartiodactyla)

The fossil record of the Hippopotamidae can shed light on three major issues in mammalian evolution. First, as the Hippopotamidae are the extant sister group of Cetacea, gaining a better understanding of the origin of the Hippopotamidae and of their Paleogene ancestors will be instrumental in clarifying phylogenetic relationships within Cetartiodactyla. Unfortunately, the data relevant to hippopotamid origins have generally been ignored in phylogenetic analyses of cetartiodactyls. In order to obtain better resolution, future analyses should consider hypotheses of hippopotamid Paleogene relationships. Notably, an emergence of the Hippopotamidae from within anthracotheriids has received growing support, leading to reconciliation between genetic and morphological evidence for the clade Cetancodonta (Hippopotamidae + Cetacea). Secondly, full account needs to be taken of the Hippopotamidae when studying the impact of environmental change on faunal evolution. This group of semi-aquatic large herbivores has a clear and distinct ecological role and a diverse and abundant fossil record, particularly in the African Neogene. We examine three major phases of hippopotamid evolution, namely the sudden appearance of hippopotamines in the late Miocene (the "Hippopotamine Event"), the subsequent rampant endemism in African basins, and the Pleistocene expansion of Hippopotamus. Each may have been influenced by multiple factors, including: late Miocene grass expansion, African hydrographical network disruption, and a unique set of adaptations that allowed Hippopotamus to respond efficiently to early Pleistocene environmental change. Thirdly, the fossil record of the Hippopotamidae documents the independent emergence of adaptive character complexes in relation to semiaquatic habits and in response to insular isolation. The semiaquatic specializations of fossil hippopotamids are particularly useful in interpreting the functional morphology and ecology of other, extinct groups of large semiaquatic herbivores. Hippopotamids can also serve as models to elucidate the evolutionary dynamics of island mammals.

Phylogeographic analysis of the mid-Holocene Mammoth from Qagnaxˆ Cave, St. Paul Island, Alaska

Phylogeographic analysis of the mid-Holocene Mammoth from Qagnaxˆ Cave, St. Paul Island, Alaska

Bionomische Beobachtungen und taxonomische Untersuchungen an Anisoptera von Cuba und dem Östlichen Mexico. (Insecta: Odonata)x

During the drier and cooler months in Cuba and eastern Mexico more than 50% of the local dragonfly species are on wing. Tab. 1 gives the record of species observed and the numbers of specimens collected during field work near Vera Cruz and Tampico as well as in the western and eastern parts of Cuba from October to the end of February in 1967/68. Two of the species mentioned (Anax concolor, Macrothermis inequiunguis) are new to the Cuban odonatofauna. The influence of storm on migrating dragonflies and the crepuscular flight of large swarms have been studied in some detail. The own material and the collections in the Berlin Zool. Museum are used for a study of the infraspecific variability of several aeshnid and libellulid species. The results indicate clear evidence of phenetic separation, different from species to species, of Cuban Erythrothemis umbrata, Lepthemis vesiculosa and Orthemis ferruginea whereas equivalent signs of insular isolation are lacking in Anax junius and Pantala flavescens. The West Indian population of Anax concolor likewise expresses a few metrical and morphological differences compared with South American specimens. The degree of detectable phenetic peculiarity of Cuban or Antillean dragonfly populations seems to be correlated with the maesure of vagility of the species concerned.

A global model of island biogeography

ABSTRACTAim The goal of our study was to build a global model of island biogeography explaining bird species richness that combines MacArthur and Wilson's area–isolation theory with the species–energy theory.Location Global.Methods We assembled a global data set of 346 marine islands representing all types of climate, topography and degree of isolation on our planet, ranging in size from 10 ha to 800,000 km2. We built a multiple regression model with the number of non‐marine breeding bird species as the dependent variable.Results We found that about 85–90% of the global variance in insular bird species richness can be explained by simple, contemporary abiotic factors. On a global scale, the three major predictors — area, average annual temperature and the distance separating the islands from the nearest continent — all have constraining (i.e. triangular rather than linear) relationships with insular bird species richness. We found that the slope of the species–area curve depends on both average annual temperature and total annual precipitation, but not on isolation. Insular isolation depends not only on the distance of an island from the continent, but also on the presence or absence of other neighbouring islands. Range in elevation — a surrogate for diversity of habitats — showed a positive correlation with bird diversity in warmer regions of the world, while its effect was negative in colder regions. We also propose a global statistical model to quantify the isolation‐reducing effect of neighbouring islands.Main conclusions The variation in avian richness among islands worldwide can be statistically explained by contemporary environmental variables. The equilibrium theory of island biogeography of MacArthur and Wilson and the species–energy theory are both only partly correct. Global variation in richness depends about equally upon area, climate (temperature and precipitation) and isolation. The slope of the species richness–area curve depends upon climate, but not on isolation, in contrast to MacArthur and Wilson's theory.

The Origin and Radiation of Macaronesian Beetles Breeding in Euphorbia: The Relative Importance of Multiple Data Partitions and Population Sampling

Species-level phylogenies derived from many independent character sources and wide geographical sampling provide a powerful tool in assessing the importance of various factors associated with cladogenesis. In this study, we explore the relative importance of insular isolation and host plant switching in the diversification of a group of bark beetles (Curculionidae: Scolytinae) feeding and breeding in woody Euphor biaspurges. All species in the genus Aphanarthrumare each associated with only one species group of Euphorbia(succulents or one of three different arborescent groups), and the majority of species are endemic to one or several of the Macaronesian Islands. Hence, putative mechanisms of speciation could be assessed by identifying pairs of sister species in a phylogenetic analysis. We used DNA sequences from two nuclear and two mitochondrial genes, and morphological characters, to reconstruct the genealogical relationships among 92 individuals of 25 species and subspecies of Aphanarthrumand related genera. A stable tree topology was highly dependent on multiple character sources, but much less so on wide population sampling. However, multiple samples per species demonstrated one case of species paraphyly, as well as deep coalescence among three putative subspecies pairs. The phylogenetic analyses consistently placed the arborescent breeding and West African--Lanzarote-distributed species A. armatumin the most basal position in Aphanarthrum, rendering this genus paraphyletic with respect to Coleobothrus. Two major radiations followed, one predominantly African lineage of succulent feeding species, and one island radiation associated with arborescent host plants. Sister comparisons showed that most recent divergences occurred in allopatry on closely related hosts, with subsequent expansions obscuring more ancient events. Only 6 out of 24 cladogenetic events were associated with host switching, rendering geographical factors more important in recent diversification.

Factors affecting Sarcocystis infection of rats on small tropical islands

The purpose of our research was to explore the limits of rat‐python‐Sarcocystis distribution among rats on the offshore tropical islands of Singapore, and to examine the effect of island size, insular isolation, landscape peculiarities and anthropogenic disturbance. Commensal rats (Rattus rattus) inhabited all of these islands, regardless of the island's size, proximity to the mainland, biogeographic features, and/or degree of anthropogenic interference. Rats caught on Sakijang Pelepah Island had well deliminated white bellies that are similar to those of sylvatic or feral rats. The prevalence of Sarcocystis spp. on individual islands ranged from 57 to 100%. This is consistent with the range found in forested habitats on Singapore Island. It also exhibited a similar diversity to Sarcocystis spp. and the predominance of Sarcocystis singaporensis. On Sakijang Pelepah Island, one rat (white bellied) was exceptionally heavily infected with both Sarcocystis villivilosi and Sarcocystis sulawesiensis. The muscles of the rats from nearly all of the islands contained immature sarcocysts, which implies that active transmission is taking place on these islands. This suggests that reticulated pythons (Python reticulatus), which are the definitive hosts of rat Sarcocystis, might have been established or frequented in all the islands of Singapore. Our study shows that the Sarcocystis infection load of the rats was negatively correlated with human disturbance, hinting that human disturbance restricts the pythons’ mobility and thus, reduces infection of Sarcocytis in the islands rats.