Human-mediated Introductions Research Articles

The role of life history traits in mammalian invasion success

Why some organisms become invasive when introduced into novel regions while others fail to even establish is a fundamental question in ecology. Barriers to success are expected to filter species at each stage along the invasion pathway. No study to date, however, has investigated how species traits associate with success from introduction to spread at a large spatial scale in any group. Using the largest data set of mammalian introductions at the global scale and recently developed phylogenetic comparative methods, we show that human‐mediated introductions considerably bias which species have the opportunity to become invasive, as highly productive mammals with longer reproductive lifespans are far more likely to be introduced. Subsequently, greater reproductive output and higher introduction effort are associated with success at both the establishment and spread stages. High productivity thus supports population growth and invasion success, with barriers at each invasion stage filtering species with progressively greater fecundity.

Comparative Phylodynamics of Rabbit Hemorrhagic Disease Virus in Australia and New Zealand.

The introduction of rabbit hemorrhagic disease virus (RHDV) into Australia and New Zealand during the 1990s as a means of controlling feral rabbits is an important case study in viral emergence. Both epidemics are exceptional in that the founder viruses share an origin and the timing of their release is known, providing a unique opportunity to compare the evolution of a single virus in distinct naive populations. We examined the evolution and spread of RHDV in Australia and New Zealand through a genome-wide evolutionary analysis, including data from 28 newly sequenced RHDV field isolates. Following the release of the Australian inoculum strain into New Zealand, no subsequent mixing of the populations occurred, with viruses from both countries forming distinct groups. Strikingly, the rate of evolution in the capsid gene was higher in the Australian viruses than in those from New Zealand, most likely due to the presence of transient deleterious mutations in the former. However, estimates of both substitution rates and population dynamics were strongly sample dependent, such that small changes in sample composition had an important impact on evolutionary parameters. Phylogeographic analysis revealed a clear spatial structure in the Australian RHDV strains, with a major division between those viruses from western and eastern states. Importantly, RHDV sequences from the state where the virus was first released, South Australia, had the greatest diversity and were diffuse throughout both geographic lineages, such that this region was likely a source population for the subsequent spread of the virus across the country. Most studies of viral emergence lack detailed knowledge about which strains were founders for the outbreak or when these events occurred. Hence, the human-mediated introduction of rabbit hemorrhagic disease virus (RHDV) into Australia and New Zealand from known starting stocks provides a unique opportunity to understand viral evolution and emergence. Within Australia, we revealed a major phylogenetic division between viruses sampled from the east and west of the country, with both regions likely seeded by viruses from South Australia. Despite their common origins, marked differences in evolutionary rates were observed between the Australian and New Zealand RHDV, which led to conflicting conclusions about population growth rates. An analysis of mutational patterns suggested that evolutionary rates have been elevated in the Australian viruses, at least in part due to the presence of low-fitness (deleterious) variants that have yet to be selectively purged.

On the origin and systematic position of the Azorean goldenrod, Solidago azorica (Asteraceae)

Goldenrods were first collected in the Azores by the German botanist Karl Hochstetter in 1838 and described as an endemic species Solidago azorica. In 1882, Asa Gray placed the name into synonymy of the American seaside goldenrod, S. sempervirens. The taxonomic position and status of the plants in the Azores remained unclear ever since but recent human-mediated introduction from the American coast seemed to be the most likely explanation. Here, I analyze molecular and morphological data and the historical record to test this hypothesis. While morphological differences are not clear and an overall similarity to some specimens from New Foundland is striking, I find that all analyzed Solidago plants from the Azores archipelago differ in their nuclear ITS and ETS sequences plus a number of microsatellite markers from American goldenrods. Furthermore, the historical record suggests existence of goldenrods in the Azores at the time of the arrival of the first settlers and well before Columbus’ first journey. Moreover, large populations were reported from several islands in the 16th century. I conclude that the Azorean plants are native to the Azores and represent a distinct endemic species sharing a common ancestor with S. sempervirens. The Azorean plants represent a geographically isolated, genetically distinct population that is most likely the result of a natural colonization event from the North American coast perhaps via vagrant birds. I reinstate the name S. azorica and describe the morphological differences between S. azorica and S. sempervirens.

Ancient and modern introduction of Broussonetia papyrifera ([L.] Vent.; Moraceae) into the Pacific: genetic, geographical and historical evidence

Broussonetia papyrifera (L.) Vent. (Moraceae), or paper mulberry, is a species of cultural importance in South East Asia, East Asia and the Pacific. Originally from mainland South East Asia or East Asia, this plant was introduced into the Pacific range by prehistoric Austronesian voyagers. We used non-coding internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA and inter-simple sequence repeat (ISSR) on 79 samples of B. papyrifera from different islands of Remote Oceania, and South East Asia and East Asia. Our results show an absence of genetic diversity in the introduced range of Remote Oceania, with the sole exception of Hawaii. By contrast, Asian samples show genetic diversity. The data obtained suggest a prehistoric human-mediated introduction of this species from East Asia to Remote Oceania and a second, possibly historic, human-mediated introduction to Hawaii.

First record and potential for red king crab Paralithodes camtschaticus (Crustacea Decapoda Lithodidae) population establishment in the White Sea

An ovigerous female of red king crab (Paralithodes camtschaticus) was caught near the White Sea Biological Station of the Zoological Institute of the Russian Academy of Sciences (Kandalaksha Bay, outer part of Chupa Inlet, Krivozerskaya Cove, Cape Kartesh) on August 21, 2013. That was the first record of the red king crab (an alien species having been established in the Barents Sea) in the inner White Sea. Earlier, this species was recorded only in the Voronka, the most distant part of the White Sea, which is substantially closer to the Barents Sea than the White Sea by its oceanographic features. The size of the female crab and its reproductive phase corresponded in general to those observed in the Barents Sea population in summer, but the quantity of developing eggs on pleopods was two order of magnitude lower than in the females of similar size in the Barents Sea. We discuss the ecological characteristics of red king crab, the possibility of its habitation in the inner White Sea, and explanations for finding of the crab specimen near Cape Kartesh. The more likely scenario is introduction by man. In the case of both human-mediated introduction and natural migration from the Voronka of the White Sea, the prospect for naturalization of P. camtschaticus in the inner White Sea is doubtful. This naturalization will be limited by low salinity in the coastal areas where crab reproduction takes place and below zero temperature of the entire water column, not allowing the finding of wintering habitats suitable for adult crab males and females.

Genetic evidence for human-mediated introduction of Anatolian water frogs (Pelophylax cf. bedriagae) to Cyprus (Amphibia: Ranidae)

We found in two water frogs captured in Cyprus, the distribution area of P. cypriensis, nuclear alleles and mitochondrial haplotypes that are characteristic of Anatolian water frogs, Pelophylax cf. bedriagae. Mitochondrial and nuclear DNA data strongly indicate that the ancestors of these two frogs did not arrive on Cyprus via a land bridge or overseas dispersal but were unintentionally introduced by humans, most probably together with carp fingerlings. Both individuals exhibited recombined nuclear genomes characteristic of backcross hybrids. Further investigations are needed to estimate the amount of introgression of allochthonous alleles into the gene pool of P. cypriensis.

Anthropocene invasion of an ecosystem engineer: resolving the history ofCorophium volutator(Amphipoda: Corophiidae) in the North Atlantic

Resolving the natural histories of species is important for the interpretation of ecological patterns, as it provides evolutionary context for the interactions between organisms and their environment. Despite playing an integral role on the intertidal mudflats of the North Atlantic as an abundant food source for predators and as an ecosystem engineer that alters the soft sediment environment, no previous studies have provided empirical evidence to determine the biogeographical origin of the amphipod Corophium volutator. To resolve its status as introduced or indigenous in Europe and North America, we analyzed sequence data for two mitochondrial loci and two nuclear markers, aiming to determine whether the present range of C. volutator is the result of unresolved taxonomy, persistence in glacial refugia, natural trans-Atlantic dispersal, or human-mediated introduction. Our results demonstrate a reduced genetic diversity in North American populations that is a subsample of diversity in European populations, with coalescent analyses of mitochondrial and nuclear DNA supporting different models of multiple introductions from Europe to the Bay of Fundy and Gulf of Maine in North America. These results suggest that C. volutator was introduced to North America prior to the first surveys of local biota in the 20th Century, which has broad implications for interpretations of community and ecosystem interactions in the North Atlantic intertidal.

Genetic structure, admixture and invasion success in a Holarctic defoliator, the gypsy moth (Lymantria dispar, Lepidoptera: Erebidae).

Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non-native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L.dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human-mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.

Beautiful, but also potentially invasive

Abstract Introduction of non-indigenous exotic species to new areas, where they may establish viable populations and become invasive, is a considerable problem in the protection of nature worldwide, as these species may alter the indigenous species population structure and potentially even decrease the biodiversity. The European fauna underwent through major negative changes on the continent and nowadays, it experiences another new treat, represented by the expanding aquarium pet trade, and with it, associated species (and disease) introductions. Exotic freshwater crustaceans are one of the taxa widely incorporated in the business, counting a remarkable number of species. Recent records of the exotic marbled crayfish or Marmorkrebs (Procambarus fallax f. virginalis) in German in open ecosystems in Slovakia pointed to human-mediated introductions associated with aquarium pet trade in the country. In this regard, a study of the aquarium pet trade both in expositions and shops and online was assessed. Several crustacean taxa are available both in pet trade exhibitions and online through the Internet. Altogether 26 different species were identified in the aquarium trade in Slovakia. These are Procambarus fallax f. virginalis, P. clarkii, P. alleni, Cherax quadricarinatus, C. destructor, C. holthuisi, C. peknyi, Cambarellus patzcuarensis and C. diminutus occurring in the aquarium pet trade in Slovakia (n = 9). Procambarus fallax f. virginalis, P. clarkii and C. patzuarensis are the most common in this regard. There is also a quantity of other related taxa in the aquarium pet trade in Slovakia, mainly Caridina spp. (n = 5), Neocaridina spp. (n = 4), Atyopsis moluccensis, Atya gabonensis, Arachnochium kulsiense and several taxa of exotic crabs (n = 5) belonging to three different genera (Cardiosoma, Geosesarma and Gecarinus) present. Neocaridina davidi is identified as the most frequent in this regard. As some of the species can become established and form viable populations in natural ecosystems in Europe, we alert the public to handle the animals responsibly and thus maintain and protect indigenous European fauna.

Phylogeny, divergence time estimation, and biogeography of the genus Heterobasidion (Basidiomycota, Russulales)

There have been several investigations into the genus Heterobasidion, however, differentiation of species in these studies have depended on the gene regions analyzed. Reliable defining of species, establishing species divergence times and establishing species biogeographical distributions have been challenging. Here, we used a multilocus phylogenetic approach and maximum parsimony, maximum likehood, and Bayesian analyses to infer the phylogenetic relationships of Heterobasidion species. In addition, we focused on a fungus fossil-based approach and used the largest subunit of RNA polymerase II-the second subunit of RNA polymerase II (RPB1-RPB2) dataset to perform maximum likelihood-based estimation and Bayesian binary analyses, to assess the divergence and biogeographical distributions of Heterobasidion species. The Heterobasidion annousum/H. insulare species complex clusters in three groups in the phylogenetic analyses. Molecular dating suggests that ancestral Heterobasidion species originated in Eurasia during the Early Miocene, followed by dispersal and speciation to other continents during the Middle Miocene and Early Pliocene. Our data are compatible with the previous viewpoint that H. irregulare and H. occidentale colonized North America via different routes, which has been interpreted as Beringian and Thulean North Atlantic vicariance. In addition, we propose that the occurrence of H. araucariae in the southern Hemisphere was probably due to recent human-mediated introductions. Plate tectonics and long-distance dispersal are the most likely factors that influenced Heterobasidion speciation and biogeography.

The naturalized flora of Brazil: a step towards identifying future invasive non-native species

Abstract Human-mediated species introductions are one of the defining factors of the Anthropocene. Non-native species can form invasive populations that affect biodiversity, ecosystem services, or farming. Here I summarized data on naturalized vascular species from the Brazilian list of seed plants and tested the hypotheses that more populated regions and biomes with less remaining natural vegetation harbor more naturalized species. The Atlantic Forest had the largest number of naturalized species, whereas the Pampa had the highest proportion of naturalized species in relation to the biome's total richness. The number of naturalized species was affected both by human population size and proportion of remaining natural vegetation. Family Poaceae had the highest numbers of naturalized species in all biomes, and, together with Asteraceae and Fabaceae, forms the top three families in number of naturalized species in five of the biomes. There were no records of species naturalized in all six biomes. However, of the 46 species naturalized in five out of six biomes, half were Poaceae. The results indicate that the Brazilian flora is currently composed both by native and naturalized species. Assessments of invasion risks and of impacts by naturalized species could help set management priorities and resource allocation towards control.

Invasion of American bullfrogs along the Yellowstone River

The American bullfrog (Lithobates catesbeianus) is a globally distributed invasive species that was introduced to the Yellowstone River floodplain of Montana. Knowledge about floodplain habitat features that allow for bullfrog persistence and spread will help identify effective control strategies. We used field surveys in 2010, 2012 and 2013 to describe bullfrog spread in the Yellowstone River floodplain and the habitat features that are associated with bullfrog occupancy and colonization. Bullfrogs in our study area expanded from ~ 60 km in 2010 to 106 km in 2013, and are spreading to up- and downstream habitats. The number of breeding sites (i.e., presence of bullfrog eggs or larvae) increased from 12 sites in 2010 to 45 sites in 2013. We found that bullfrogs were associated with deeper waters, emergent vegetation and public-access sites, which are habitat features that characterize permanent waters and describe human-mediated introductions. Control strategies that reduce the hydroperiod of breeding sites may help to limit bullfrog persistence and spread, while an increase in public outreach and education may help prevent further bullfrog introductions at public-access sites.

Elucidating the phylodynamics of endemic rabies virus in eastern Africa using whole-genome sequencing.

Many of the pathogens perceived to pose the greatest risk to humans are viral zoonoses, responsible for a range of emerging and endemic infectious diseases. Phylogeography is a useful tool to understand the processes that give rise to spatial patterns and drive dynamics in virus populations. Increasingly, whole-genome information is being used to uncover these patterns, but the limits of phylogenetic resolution that can be achieved with this are unclear. Here, whole-genome variation was used to uncover fine-scale population structure in endemic canine rabies virus circulating in Tanzania. This is the first whole-genome population study of rabies virus and the first comprehensive phylogenetic analysis of rabies virus in East Africa, providing important insights into rabies transmission in an endemic system. In addition, sub-continental scale patterns of population structure were identified using partial gene data and used to determine population structure at larger spatial scales in Africa. While rabies virus has a defined spatial structure at large scales, increasingly frequent levels of admixture were observed at regional and local levels. Discrete phylogeographic analysis revealed long-distance dispersal within Tanzania, which could be attributed to human-mediated movement, and we found evidence of multiple persistent, co-circulating lineages at a very local scale in a single district, despite on-going mass dog vaccination campaigns. This may reflect the wider endemic circulation of these lineages over several decades alongside increased admixture due to human-mediated introductions. These data indicate that successful rabies control in Tanzania could be established at a national level, since most dispersal appears to be restricted within the confines of country borders but some coordination with neighbouring countries may be required to limit transboundary movements. Evidence of complex patterns of rabies circulation within Tanzania necessitates the use of whole-genome sequencing to delineate finer scale population structure that can that can guide interventions, such as the spatial scale and design of dog vaccination campaigns and dog movement controls to achieve and maintain freedom from disease.

Genetics reveal the origin and timing of a cryptic insular introduction of muskrats in North America.

The muskrat, Ondatra zibethicus, is a semiaquatic rodent native to North America that has become a highly successful invader across Europe, Asia, and South America. It can inflict ecological and economic damage on wetland systems outside of its native range. Anecdotal evidence suggests that, in the early 1900s, a population of muskrats was introduced to the Isles of Shoals archipelago, located within the Gulf of Maine, for the purposes of fur harvest. However, because muskrats are native to the northeastern coast of North America, their presence on the Isles of Shoals could be interpreted as part of the native range of the species, potentially obscuring management planning and biogeographic inferences. To investigate their introduced status and identify a historic source population, muskrats from Appledore Island of the Isles of Shoals, and from the adjacent mainland of Maine and New Hampshire, were compared for mitochondrial cytochrome b sequences and allele frequencies at eight microsatellite loci. Appledore Island muskrats consistently exhibited reduced genetic diversity compared with mainland populations, and displayed signatures of a historic bottleneck. The distribution of mitochondrial haplotypes is suggestive of a New Hampshire source population. The data presented here are consistent with a human-mediated introduction that took place in the early 1900s. This scenario is further supported by the zooarchaeological record and island biogeographic patterns. This is the first genetic study of an introduced muskrat population within US borders and of any island muskrat population, and provides an important contrast with other studies of introduced muskrat populations worldwide.

Establishment of Chydorus sphaericus (O.F. Muller, 1785) (Crustacea: Cladocera) in Australia: consequences of mass fish stocking from Northern Europe?

There are 11 species of genus Chydorus Leach, 1816 (Cladocera: Chydoridae) in Australia, including populations of Chydorus sphaericus (O.F. Müller, 1785) morphologically undistinguishable from European ones. Our genetic study of C. sphaericus from two large artificial water bodies in the Adelaide region of South Australia led us to conclude the taxon was introduced to Australia from Europe by human activity, at least in the two studied water bodies. To provide a comprehensive sister-taxa coverage and survey of intraspecific variation, our data were complemented by sequences on Chydorus sphaericus-group from GenBank and Barcode of Life Data Systems website. We speculate that it was related to a mass stocking of introduced species of fishes from Europe. To confirm whether C. sphaericus is an invasive species due to human-mediated introductions, or whether it is a native Australian taxon, further extensive molecular studies (involving nuclear genes) and detailed morphological comparisons are needed. This is a first report on the invasion of a non-daphniid species of Cladocera to Australia. Its significance for Australian ecosystems needs special future studies.

Visibility from roads predict the distribution of invasive fishes in agricultural ponds.

Propagule pressure and habitat characteristics are important factors used to predict the distribution of invasive alien species. For species exhibiting strong propagule pressure because of human-mediated introduction of species, indicators of introduction potential must represent the behavioral characteristics of humans. This study examined 64 agricultural ponds to assess the visibility of ponds from surrounding roads and its value as a surrogate of propagule pressure to explain the presence and absence of two invasive fish species. A three-dimensional viewshed analysis using a geographic information system quantified the visual exposure of respective ponds to humans. Binary classification trees were developed as a function of their visibility from roads, as well as five environmental factors: river density, connectivity with upstream dam reservoirs, pond area, chlorophyll a concentration, and pond drainage. Traditional indicators of human-mediated introduction (road density and proportion of urban land-use area) were alternatively included for comparison instead of visual exposure. The presence of Bluegill (Lepomis macrochirus) was predicted by the ponds' higher visibility from roads and pond connection with upstream dam reservoirs. Results suggest that fish stocking into ponds and their dispersal from upstream sources facilitated species establishment. Largemouth bass (Micropterus salmoides) distribution was constrained by chlorophyll a concentration, suggesting their lower adaptability to various environments than that of Bluegill. Based on misclassifications from classification trees for Bluegill, pond visual exposure to roads showed greater predictive capability than traditional indicators of human-mediated introduction. Pond visibility is an effective predictor of invasive species distribution. Its wider use might improve management and mitigate further invasion. The visual exposure of recipient ecosystems to humans is important for many invasive species that spread with frequent instances of human-mediated introduction.

Cryptic diversity of Melanochlamys sea slugs (Gastropoda, Aglajidae) in the North Pacific

North Pacific specimens of Melanochlamys sea slugs were examined morphologically (including the male reproductive morphology, shell and external coloration) and were sequenced for three genes (mitochondrial COI and 16S and nuclear H3). Phylogenetic and species delimitation analyses were used to determine the evolutionary relationships and species diversity among the specimens examined. Both molecular and morphological data revealed an unexpected high level of cryptic diversity. At least four distinct species occur on the Northwestern Pacific. Melanochlamys ezoensis occurs in Russia and temperate and cold areas in Japan. Three additional undescribed species occur in Japan and/or South Korea. One of the undescribed species occurs both in South Korea and in Japan, but only in Tokyo Bay, suggesting that it could be non‐native in Japan. Two distinct species occur on the Northeastern Pacific coast; Melanochlamys diomedea is widespread from Southern California to Alaska, whereas M. ezoensis was found only in San Francisco Bay, suggesting a human‐mediated introduction. This is further supported by the absence of records of M. ezoensis in San Francisco prior to 2001. The species diversity of Melanochlamys in the Northwestern Pacific is much greater than in the Northeastern Pacific; it is hypothesized that differences in geographic and ocean current system complexity might account for different responses to glacial extinction and postglacial expansion.

Unexpected population genetic structure of European roe deer in Poland: an invasion of the mtDNA genome from Siberian roe deer

Introgressive hybridization is a widespread evolutionary phenomenon which may lead to increased allelic variation at selective neutral loci and to transfer of fitness-related traits to introgressed lineages. We inferred the population genetic structure of the European roe deer (Capreolus capreolus) in Poland from mitochondrial (CR and cyt b) and sex-linked markers (ZFX, SRY, DBY4 and DBY8). Analyses of CR mtDNA sequences from 452 individuals indicated widespread introgression of Siberian roe deer (C. pygargus) mtDNA in the European roe deer genome, 2000 km from the current distribution range of C. pygargus. Introgressed individuals constituted 16.6% of the deer studied. Nearly 75% of them possessed haplotypes belonging to the group which arose 23 kyr ago and have not been detected within the natural range of Siberian roe deer, indicating that majority of present introgression has ancient origin. Unlike the mtDNA results, sex-specific markers did not show signs of introgression. Species distribution modelling analyses suggested that C. pygargus could have extended its range as far west as Central Europe after last glacial maximum. The main hybridization event was probably associated with range expansion of the most abundant European roe deer lineage from western refugia and took place in Central Europe after the Younger Dryas (10.8-10.0 ka BP). Initially, introgressed mtDNA variants could have spread out on the wave of expansion through the mechanism of gene surfing, reaching high frequencies in European roe deer populations and leading to observed asymmetrical gene flow. Human-mediated introductions of C. pygargus had minimal effect on the extent of mtDNA introgression.

Critically endangered island endemic or peripheral population of a widespread species? Conservation genetics of Kikuchi's gecko and the global challenge of protecting peripheral oceanic island endemic vertebrates

Aim To highlight the significant conservation challenge of evaluating peripheral endemic vertebrates in island archipelago systems and to assess empirically the complexities of approaches to conservation genetic studies across political and biogeographic boundaries. To demonstrate the poignant need for international collaboration and coordination when species delimitation problems with high conservation concern involve island endemics with biogeographically peripheral ranges. Location Southeast Asia, Lanyu Island, Taiwan, and the Philippines. Methods Genetic samples were collected and sequenced for one mitochondrial gene and five nuclear loci for species of the Gekko mindorensis-G. kikuchii species complex in Southeast Asia. We used maximum likelihood and Bayesian phylogenetic methods and coalescent-based species delimitation analyses to estimate phylogeographic relationships, construct multilocus haplotype networks and test putative species boundaries. Results Phylogenetic and population genetic analyses suggest that Kikuchi's Gecko may represent a peripheral population of a widespread species distributed from the northern Philippines to Taiwan. However, we identify a discrepancy between inferences of species boundaries resulting from methods based on allele frequencies versus coalescent-based methods that incorporate evolutionary history. Coalescent-based analyses suggest that G. kikuchii may be a distinct evolutionary lineage. Our study underscores the need for coalescent-based methods in conjunction with population genetic approaches for conservation genetic assessments of widespread species. Main conclusions This study joins a few recent works suggesting that Philippine-derived anomalies in the fauna of Lanyu (and possibly greater Taiwan) are worthy of careful reconsideration. Determining whether each is the result of recent human-mediated introduction or (possibly more ancient) natural dispersal should be the goal of future studies on this seldom-conceived biogeographic relationship. Isolated species endemic to islands on the outer periphery of biogeographic and political regions represent particular conservation challenges. This is especially true if a species occurs on an isolated island that is allied biogeographically with one nation, but politically administered by another.

A Multidisciplinary Approach to the Analysis of Multifactorial Land Mammal Colonization of Islands

A highly debated question that engages paleontologists, zoogeographers, and zoologists is how terrestrial mammals colonize islands. The question’s oversimplification and the subjective and partial responses to it have led to reductionist models. Insular faunas and fossil assemblages result from a complex interaction of geological, biological (in a broad sense), climatic, eustatic, taphonomic, and historical processes. Insular assemblages and their accompanying variables should be investigated on a case-by-case basis. In this article, we discuss not only common misconceptions and their potential origins but also the key issues that should be addressed when dealing with the colonization of islands by land mammals. We call for the implementation of multi- and interdisciplinary research programs and teamwork, involving paleontological, geological, and stratigraphic information; climatological factors; sea-level evolution; sampling and analytical biases; ecological, physiological, taphonomic, and environmental factors; behavioral characters and ecological preferences; genetics; phylogeography; densities of colonizing populations; and historical reports of human-mediated faunal introductions.