The effect of mainland dynamics on data and parameter estimates in island biogeography

Understanding macroevolution on islands requires knowledge of the closest relatives of island species on the mainland. The evolutionary relationships between island and mainland species can be reconstructed using phylogenies, to which models can be fitted to understand the dynamical processes of colonisation and diversification. But how much information on the mainland is needed to gain insight into macroevolution on islands? Here we first test whether species turnover on the mainland and incomplete mainland sampling leave recognisable signatures in community phylogenetic data. We find predictable phylogenetic patterns: colonisation times become older and the perceived proportion of endemic species increases as mainland turnover and incomplete knowledge increase. We then analyse the influence of these factors on the inference performance of the island biogeography model DAISIE, a whole-island community phylogenetic model that assumes that mainland species do not diversify, and that the mainland is fully sampled in the phylogeny. We find that colonisation and diversification rate are estimated with little bias in the presence of mainland extinction and incomplete sampling. By contrast, the rate of anagenesis is overestimated under high levels of mainland extinction and incomplete sampling, because these increase the perceived level of island endemism. We conclude that community-wide phylogenetic and endemism datasets of island species carry a signature of mainland extinction and sampling. The robustness of parameter estimates suggests that island diversification and colonisation can be studied even with limited knowledge of mainland dynamics.

Island biogeography theory and the urban landscape: stopover site selection by the silver-haired bat (Lasionycteris noctivagans)

Many migratory bats require forested sites for roosting and foraging along their migration path, but increased urbanization and intensive agricultural practices may reduce the availability of stopover sites. Urban forests may provide important stopover habitat, maintaining landscape connectivity in regions where the majority of natural habitat has been cleared for development. Island biogeography theory can be applied to urbanized temperate forest biomes where small urban forests represent islands separated from the larger “mainland” forest. We used acoustic monitoring during the fall migration period to investigate the use of urban forest habitat by the migratory species Lasionycteris noctivagans Le Conte, 1831. We predicted that recorded activity would have a positive relationship with forest patch area and shape and a negative relationship with isolation from other forest patches, as suggested by island biogeography theory. We observed greater activity at larger forest patches, and although relationships for shape and isolation were not statistically supported the observed patterns were consistent with predictions. Our results demonstrate the need for more in-depth research on the habitat requirements for both migratory and resident bat species and the impact that ongoing urbanization has on local bat populations.

Genomes of keystone Mortierella species lead to better in silico prediction of soil mycobiome functions from Taiwan's offshore islands

The ability to correlate the functional relationship between microbial communities and their environment is critical to understanding microbial ecology. There is emerging knowledge on island biogeography of microbes but how island characteristics influence functions of microbial community remain elusive. Here, we explored soil mycobiomes from nine islands adjacent to Taiwan using ITS2 amplicon sequencing. Geographical distances and island size were positively correlated to dissimilarity in mycobiomes, and we identified 56 zero-radius operational taxonomic units (zOTUs) that were ubiquitously present across all islands, and as few as five Mortierella zOTUs dominate more than half of mycobiomes. Correlation network analyses revealed that seven of the 45 hub species were part of the ubiquitous zOTUs belonging to Mortierella, Trichoderma, Aspergillus, Clonostachys and Staphylotrichum. We sequenced and annotated the genomes of seven Mortierella isolates, and comparative predictions of KEGG orthologues using PICRUSt2 database updated with new genomes increased sequence reads coverage by 62.9% at the genus level. In addition, genes associated with carbohydrate and lipid metabolisms were differentially abundant between islands which remained undetected in the original database. Predicted functional pathways were similar across islands despite their geographical separation, difference in differentially abundant genes and composition. Our approach demonstrated the incorporation of the key taxa genomic data can improve functional gene prediction results and can be readily applied to investigate other niches of interests.

Contemporizing island biogeography theory with anthropogenic drivers of species richness

Classic ecological theory must explain effects of humans on biodiversity to be more applicable today. We contemporized island biogeographic theory providing native, introduced, and total species richness relationship expectations with natural and anthropogenic metrics of habitat diversity (geographic and economic area) and isolation from source pools (geographic and economic isolation). We assessed these expectations across Caribbean island herpetofauna clades. As expected by the contemporized theory, natural habitat diversity metrics exhibited positive relationships with native and introduced richness, strengthening positive total richness-area relationships. Geographic isolation exhibited negative relationships with native and positive relationships with introduced richness, weakening total richness-isolation relationships. Economic area and isolation exhibited negative and positive relationships, respectively, with native richness but positive and negative relationships, respectively, with introduced richness. Total richness relationships with economic area and isolation were strongest in clades with many introductions. As more species spread globally, these contemporary expectations will increasingly predict Anthropocene island biogeography.

The Theory of Island Biogeography on the Hawaiki Archipelago

<p>This thesis addresses MacArthur and Wilson‟s Theory of Island Biogeography (1967) on a set of islands around the north-east coast of the North Island of New Zealand. The flora species lists from these islands were obtained from both published and unpublished island surveys whilst Geographical Information Systems (GIS) techniques were utilised in order to calculate the physical geography of islands. These islands were an ideal study site for such research because they display natural gradients in both physical geography as well as native and exotic species richness. The literature on the Theory of Island Biogeography has yet to comprehensively understand the differences between the patterns of exotic richness and native richness. Furthermore, the importance of studies on exotics species is increasingly relevant given the negative effect they have had on native communities worldwide. The results of my research illustrated that there were similar species-area and species-isolation relationships between exotic and native species. These two relationships were also consistent with what is expected under classical island biogeography principles. Interestingly however, I found that distance from the mainland had a stronger negative effect on exotics species. There were a significantly lower proportion of exotics with increasing isolation. This result has applicable outcomes for conservation management on the Hawaiki archipelago. I suggested that weeding effort focus on larger islands and in particular the islands closer to the mainland. Globally, the biogeographical patterns of exotic species are still poorly examined. With insights from this study and other similar research the Theory of Island Biogeography may be an informative approach to dealing with the ominous threat of exotic species.</p>

The Theory of Island Biogeography on the Hawaiki Archipelago

<p>This thesis addresses MacArthur and Wilson‟s Theory of Island Biogeography (1967) on a set of islands around the north-east coast of the North Island of New Zealand. The flora species lists from these islands were obtained from both published and unpublished island surveys whilst Geographical Information Systems (GIS) techniques were utilised in order to calculate the physical geography of islands. These islands were an ideal study site for such research because they display natural gradients in both physical geography as well as native and exotic species richness. The literature on the Theory of Island Biogeography has yet to comprehensively understand the differences between the patterns of exotic richness and native richness. Furthermore, the importance of studies on exotics species is increasingly relevant given the negative effect they have had on native communities worldwide. The results of my research illustrated that there were similar species-area and species-isolation relationships between exotic and native species. These two relationships were also consistent with what is expected under classical island biogeography principles. Interestingly however, I found that distance from the mainland had a stronger negative effect on exotics species. There were a significantly lower proportion of exotics with increasing isolation. This result has applicable outcomes for conservation management on the Hawaiki archipelago. I suggested that weeding effort focus on larger islands and in particular the islands closer to the mainland. Globally, the biogeographical patterns of exotic species are still poorly examined. With insights from this study and other similar research the Theory of Island Biogeography may be an informative approach to dealing with the ominous threat of exotic species.</p>