α- and β-Diversity Patterns of Macrophytes and Freshwater Fishes are Driven by Different Factors and Processes in Lakes of the Unexplored Southern Balkan Biodiversity Hotspot

Anthi Oikonomou,Konstantinos Stefanidis

doi:10.3390/w12071984

Abstract

Disentangling the main drivers of species richness and community composition is a central theme in ecology. Freshwater biodiversity patterns have been poorly explored; yet, it has been shown that different freshwater biota have different, often contrasting responses to environmental gradients. In this study, we investigated the relative contribution of geographical and environmental (habitat-, climate- and water quality-related) factors/gradients in shaping the α- and β-diversity patterns of macrophytes and fish in sixteen natural freshwater lakes of an unexplored Balkan biodiversity hotspot, the Southern Balkan Peninsula. We employed generalized linear modeling to identify drivers of α-diversity, and generalized dissimilarity modeling to explore commonalities and dissimilarities of among-biota β-diversity. Species richness of both biota was significantly associated with lake surface area, whereas macrophytes had an inverse response to altitude, compared to fish. Both species turnover and nestedness significantly contributed to the total β-diversity of macrophytes. In contrast, species turnover was the most significant contributor to the total fish β-diversity. We found that the compositional variation of macrophytes is primarily limited by dispersal and ultimately shaped by environmental drivers, resulting in spatially structured assemblages. Fish communities were primarily shaped by altitude, highlighting the role of species sorting. We conclude that among-biota diversity patterns are shaped by different/contrasting factors, and, thus, effective/sustainable conservation strategies should encompass multiple aquatic biota.

Highlights

For α- diversity, various historical, environmental, and geographical factors [11] have long been recognized as major drivers, with their relative importance being the key approach to understanding the mechanisms and rules of community assembly [12,13]
We developed Generalized Dissimilarity Models (GDMs) to evaluate the relative contribution of environmental and geographical factors in explaining variation in the three β-diversity components, hypothesizing that passively dispersing organisms with good dispersal ability would be subject to stronger environmental control/filtering than actively dispersing organisms across the Southern Balkan lakes
We found that fish species richness decreases substantially until the elevation of 400 m, above which it shows small changes, whereas aquatic macrophyte richness increases with altitude showing highest rates of change between sea level and altitudes of about 200 m

Summary

Introduction

Ecological research has shifted focus from exploring local (termed α-diversity) or regional species richness patterns (termed γ-diversity) to understanding how species composition varies spatially (termed β-diversity) and which factors may generate such variation [5,6,7,8,9,10]. For α- diversity, various historical, environmental, and geographical factors [11] have long been recognized as major drivers, with their relative importance being the key approach to understanding the mechanisms and rules of community assembly [12,13]. For β-diversity, studies have shown that environmental filtering is the strongest mechanism, responsible for high compositional dissimilarities, as species sort themselves along environmental gradients [14,15,16,17,18].

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Results

Conclusion