Climate drives community-wide divergence within species over a limited spatial scale: evidence from an oceanic island

Geographic isolation substantially contributes to species endemism on oceanic islands when speciation involves the colonisation of a new island. However, less is understood about the drivers of speciation within islands. What is lacking is a general understanding of the geographic scale of gene flow limitation within islands, and thus the spatial scale and drivers of geographical speciation within insular contexts. Using a community of beetle species, we show that when dispersal ability and climate tolerance are restricted, microclimatic variation over distances of only a few kilometres can maintain strong geographic isolation extending back several millions of years. Further to this, we demonstrate congruent diversification with gene flow across species, mediated by Quaternary climate oscillations that have facilitated a dynamic of isolation and secondary contact. The unprecedented scale of parallel species responses to a common environmental driver for evolutionary change has profound consequences for understanding past and future species responses to climate variation

Recent geospatial dynamics of Terceira (Azores, Portugal) and the theoretical implications for the biogeography of active volcanic islands

Ongoing work shows that species richness patterns on volcanic oceanic islands are shaped by surface area changes driven by longer time scale (>1 ka) geological processes and natural sea level fluctuations. A key question is: what are the rates and magnitudes of the forces driving spatial changes on volcanic oceanic islands which in turn affect evolutionary and biogeographic processes? We quantified the rates of surface-area changes of a whole island resulting from both volcanogenic flows and sea level change over the last glacial-interglacial (GI) cycle (120 ka) for the volcanically active island of Terceira, (Azores, Macaronesia, Portugal). Volcanogenic activity led to incidental but long-lasting surface area expansions by the formation of a new volcanic cone and lava-deltas, whereas sea level changes led to both contractions and expansions of area. The total surface area of Terceira decreased by as much as 24% per time step due to changing sea levels and increased by 37% per time step due to volcanism per time step of 10 ka. However, while sea levels nearly continuously changed the total surface area, volcanic activity only impacted total surface area during two time steps over the past 120 ka. The surface area of the coastal and lowland region (here defined as area [removed

Correspondence : Smith (William) and Engelmann (George), 1876.

Smith, (William) to Engelmann, 187

Island biodiversity conservation needs palaeoecology

The discovery and colonization of islands by humans has invariably resulted in their widespread ecological transformation. The small and isolated populations of many island taxa, and their evolution in the absence of humans and their introduced taxa, mean that they are particularly vulnerable to human activities. Consequently, even the most degraded islands are a focus for restoration, eradication, and monitoring programmes to protect the remaining endemic and/or relict populations. Here, we build a framework that incorporates an assessment of the degree of change from multiple baseline reference periods using long-term ecological data. The use of multiple reference points may provide information on both the variability of natural systems and responses to successive waves of cultural transformation of island ecosystems, involving, for example, the alteration of fire and grazing regimes and the introduction of non-native species. We provide exemplification of how such approaches can provide valuable information for biodiversity conservation managers of island ecosystems

Forging Ahead By Land and By Sea: Archaeology and Paleoclimate Reconstruction in Madagascar

Madagascar is an exceptional example of island biogeography. Though a large island, Madagascar’s landmass is small relative to other places in the world with comparable levels of biodiversity, endemicity, and topographic and climatic variation. Moreover, the timing of Madagascar’s human colonization and the social-ecological trajectories that followed human arrival make the island a unique case study for understanding the dynamic relationship between humans, environment, and climate. These changes are most famously illustrated by the mass extinction of the island’s megafauna but also include a range of other developments. Given the chronological confluence of human arrival and dramatic transformations of island ecologies, one of the most important overarching questions for research on Madagascar is how best to understand the interconnections between human communities, the environment, and climate. In this review paper, we contribute to the well-established discussion of this complex question by highlighting the potential for new multidisciplinary research collaborations in the southwest part of the island. Specifically, we promote the comparison of paleoclimate indicators from securely dated archaeological and paleontological contexts with Western Indian Ocean climate records, as a productive way to improve the overall resolution of paleoclimate and paleoenvironmental reconstruction for the island. Given new archaeological findings that more than double the length of Madagascar’s human occupation, models of environmental transformation post-human arrival must be reassessed and allow for the possibility of slower and more varied rates of change. Improving the spatial and temporal resolution of paleoclimate reconstruction is critical in distinguishing anthropogenic and climate drivers of environmental change. It will also increase our capacity to leverage archaeological and paleoclimate research toward resolving modern challenges, such as environmental conservation and poverty alleviation