Identification of metacommunities in bioregions with historical habitat networks

Abstract

Although metacommunity theory provides many useful insights for conservation planning, the transfer of this knowledge to practice is hampered due to the difficulty of identifying metacommunities in bioregions. This study aims to identify the spatial extent of metacommunities at bioregional scales using current and historical habitat data, especially because contemporary biodiversity patterns may be a result of time-lagged responses to historical habitat configurations. Further, this estimation of the metacommunity spatial extent is based on both the habitat structure and the dispersal ability of the species. Focusing on dragonfly and damselfly (odonate) species in the eastern Swiss Plateau, the research uses wetland habitat information spanning over 110 years to create a time series of nine habitat networks between 1899 and 2010. From these networks, we identified the spatial extents of metacommunities based on the year of habitat information as well as on watershed boundaries. To identify the best metacommunity spatial extents, the study investigates whether patch pairs within a metacommunity exhibit greater similarity in species composition (i.e. lower beta-diversity) than patch pairs between metacommunities. For the different metacommunities, we further investigated correlations between gamma diversity and metacommunity size and compare them to theoretical expectations. In both analyses we found that augmenting spatial metacommunity identification with historical geographical proximity results in stronger associations with biodiversity patterns (beta and gamma diversity) than when using only current-day habitat or watershed information.

Keywords: biodiversity; conservation; habitat networks; landscape history; metacommunity.

FIGURE 1

(a) Map of the study area, that is the Eastern Swiss Plateau region (black line) with a 15 km buffer (shaded red) indicating the study area; (b) A zoomed in map of the habitat patches for the region around the city of Zurich both for the current time step (2010) and an historical time step (1899); (c) Schematic overview of how the metacommunity spatial extents are delineated based on connected patched that fall within a species dispersal threshold; (d) Schematic overview patch pairs sorted into ‘within’ and ‘between’ categories based on the metacommunity spatial extents along with exemplary boxplots used to assess the best delineation.

FIGURE 2

Results showing classification accuracy of different historical (Networkxxxx, where xxxx stands for the year), current (Network2010) and watershed (WS) based metacommunity clusters for within‐ and between‐metacommunity beta‐diversity at 500 m dispersal threshold (a) boxplots of the ‘Within’ and ‘Between’ categories of patch pairs and their corresponding beta‐diversity distributions; (b) Kappa scores, Accuracy and Precision metrics for the classification; Red dotted box shows networks with relatively high Kappa values and yellow dotted box shows the 2010 (current) network.

FIGURE 3

(a) Decrease in wetland cover from 1899 until 2010 with metacommunity boundaries (black polygons); (b) Change in mean no. of patches and mean area of patches (based on 500 m maximum dispersal) over 1899–2010 for all metacommunities with odonate species data available.

FIGURE 4

Scatter plots showing the relationship between log transformed (a) patch area, (b) no. of patches and (c) network diameter of metacommunities with corresponding regional (gamma) diversity for both historical (1899) and current (2010) metacommunities. Pearson correlation values and corresponding p‐values (in brackets) are shown in the scatterplots.