Spatiotemporal dynamics of tropical bats in a land-bridge island system: a 20-year assessment

Destruction and degradation of natural ecosystems are key drivers of global biodiversity decline1. In modified landscapes, natural habitats are typically divided into isolated fragments that are surrounded by a human-altered matrix. Habitat fragmentation can have detrimental effects on both the function and structure of ecosystems. Forest ecosystems in particular harbour high levels of biodiversity, yet 70% of remaining forests are within 1 km of a habitat edge. Forest fragments are less stable in microclimatic conditionsand are more susceptible to edge effects. Despite this, the rate of global forest loss continues to increase 3,6 as our per capita demand grows. Understanding how biodiversity responds to habitat fragmentation is key to implementing successful conservation strategies as we continue to alter landscapes.

The land-bridge islands in Panama's Gatún Lake provide an ideal setting to study the temporal effects of fragmentation after the creation of the islands around 100 years ago. Extensive fieldwork was conducted to collect bat occurrence and abundance data of over 8000 bats across 11 island and 6 mainland sites within the area surrounding Barro Colorado Island two decades ago. This dataset provides a unique and powerful foundation to conduct a comparative analysis
to evaluate how the taxonomic, functional and phylogenetic diversity of bats has changed since then.

I aim to investigate the long-term effect of fragmentation on the taxonomic, functional and phylogenetic diversity of bat assemblages, and assess functional and phylogenetic-area relationships21,22. To our knowledge, no studies have jointly looked at the long-term patterns of taxonomic, functional and phylogenetic bat diversity on forest fragments surrounded by static matrix. Using the Gatún Lake islands as a system to better understand the long-term effects of
fragmentation on biodiversity within static matrices may be used to heed a warning of the potential long-term effects of fragmentation within other fragmented systems surrounded by less favourable matrices, such as forest fragments within urban settings. Exploring the temporal dimension of biodiversity response to fragmentation may offer a unique and powerful insight, which in turn can inform conservation decision making to best support biodiversity within human-modified landscape