Patterns and processes in complex landscapes: testing alternative biogeographical hypotheses through integrated analysis of phylogeography and community ecology in Hawai'i

Abstract

The Island of Hawai'i is a dynamic assemblage of five volcanoes with wet forest habitat currently existing in four distinct natural regions that vary in area, age and geographical isolation. In this complex landscape, alternative assumptions of the relative importance of specific habitat characteristics on evolutionary and ecological processes predict strikingly different general patterns of local diversity and regional similarity. In this study, we compare alternative a priori hypotheses against observed patterns within two distinct biological systems and scales: community composition of wet forest vascular plant species and mitochondrial and nuclear genes of Drosophila sproati, a wet-forest-restricted endemic. All observed patterns display strong and similar regional structuring, with the greatest local diversity found in Kohala and the windward side of Mauna Loa, the least in Ka'ū and Kona, and a distinctive pattern of regional similarity that probably reflects the historical development of this habitat on the island. These observations largely corroborate a biogeographical model that integrates multiple lines of evidence, including climatic reconstruction, over those relying on single measures, such as current habitat configuration or substrate age. This method of testing alternative hypotheses across biological systems and scales is an innovative approach for understanding complex landscapes and should prove valuable in diverse biogeographical systems.

Hawaiian picture‐winged Drosophila exhibit adaptive population divergence along a narrow climatic gradient on Hawaii Island

“…However, the populations were housed in the same common environment room for five generations before the initiation of this study, which should limit any epigenetic effects. Since D. sproati are large and able fliers, and the previous island‐wide study did not find genetic structuring within the larger wet forest region on the eastern side of Hawaii Island (Eldon et al, ), divergent adaptation amidst ongoing gene flow appears to be the most parsimonious explanation for our observations.…”

“…DNA was extracted from all wild‐caught flies using a nondestructive soaking technique specially developed for arthropods (Rowley et al, ) and subsequently purified with a Qiagen DNeasy kit (Qiagen, Hilden, Germany) and stored at −20°C. Between‐population genetic differentiation was measured using the mitochondrial cytochrome oxidase II gene (COII) and nuclear yolk protein I gene (YPI) as described in Eldon et al, . These two genes showed no significant differentiation within D. sproati sampled among multiple locations within the large eastern wet forest region of Hawaii Island that encompasses the study site (Eldon et al, , unpublished data).…”

“…Between‐population genetic differentiation was measured using the mitochondrial cytochrome oxidase II gene (COII) and nuclear yolk protein I gene (YPI) as described in Eldon et al, . These two genes showed no significant differentiation within D. sproati sampled among multiple locations within the large eastern wet forest region of Hawaii Island that encompasses the study site (Eldon et al, , unpublished data). Sequencher version 4.9 was used to visually aligned and edit sequences and Arlequin version 3.1 was used to perform all statistical analysis of these two gene regions (Excoffier, Laval, & Schneider, ).…”

Multiple, independent colonizations of the Hawaiian Archipelago by the family Dolichopodidae (Diptera)

“…However, even within this iconic group, there are examples and it has been very well studied in the sympatric sibling pair D. silvestris and D. heteroneura (Carson, 1982; DeSalle et al, 1987; Price & Boake, 1995). Newer examples are now accumulating across taxonomic groups (e.g., Goodman, Welter & Roderick, 2012; Eldon et al, 2013; Bennett & O’Grady, 2013; Liebherr, 2015), exposing how variable a process diversification can be, and how dependent it is on the dispersal capabilities of the groups studied (Price & Wagner, 2004). The Eurynogaster complex shows at least five instances of within-island diversification.…”

Integrating a Population Genomics Focus into Biogeographic and Macroecological Research

“…By simultaneously studying biogeographic species patterns and population genetic data, these authors gained novel insights into the processes structuring patterns of spatial diversity. Other studies combining genetic with biogeographic and/or macroecological data have made similar advances in inferring the processes underlying spatial diversity (e.g., Bonada et al, 2009;Thiel-Egenter et al, 2011;Eldon et al, 2013).…”