Peeling the Layers of Caddisfly Diversity on a Longitudinal Gradient in Karst Freshwater Habitats Reveals Community Dynamics and Stability.

Ivana Pozojević,Marija Ivković,Ana Previšić,Katarina Ana Cetinić

doi:10.3390/insects12030234

Ivana Pozojević, Marija Ivković + Show 2 more

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https://doi.org/10.3390/insects12030234

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Journal: Insects	Publication Date: Mar 10, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: University of Zagreb, Rudjer Boskovic Institute

Abstract

Simple SummaryFreshwater biodiversity is facing a severe crisis due to many different human-caused impacts, such as climate change, pollution, habitat alterations, etc. Aquatic insects are one of the most important bioindicators used in freshwater ecological quality assessment systems, yet knowledge on diversity dynamics of their communities is incomplete. In the current study, we compare and evaluate performance of different diversity measures, i.e., commonly used simple diversity indices vs. novel complex measures incorporating ecological information of species (feeding behavior and stream zonation preferences). As a target group, we chose caddisflies, a species-rich, aquatic insect order, in different habitats of an anthropogenically unimpacted, connected karst barrage lake/riverine system. In line with our hypothesis, the complex diversity measures were more efficient in ranking and distinguishing different habitats, particularly the ones with similar communities. We also constructed a novel measure to rank the habitats by sensitivity to climate change, based on diversity of caddisfly communities and vulnerability of species inhabiting them. As expected, the springs were ranked as most vulnerable habitats. Our study further underlines the importance of integrating ecological information into biodiversity and vulnerability assessment of freshwater communities.Freshwater biodiversity is facing a severe crisis due to many human impacts, yet the diversity dynamics of freshwater communities and possibilities of assessing these are vastly unexplored. We aimed at emphasizing different aspects of portraying diversity of a species-rich, aquatic insect group (caddisflies; Trichoptera) across four different habitats in an anthropogenically unimpacted, connected karst barrage lake/riverine system. To define diversity, we used common indices with pre-set sensitivity to species abundance/dominance; i.e., sensitivity parameter (species richness, Shannon, Simpson, Berger-Parker) and diversity profiles based on continuous gradients of this sensitivity parameter: the naïve and non-naïve diversity profiles developed by Leinster and Cobbold. The non-naïve diversity profiles show diversity profiles with regard to the similarity among species in terms of ecological traits and preferences, whereas the naïve diversity profile is called mathematically “naïve” as it assumes absolute dissimilarity between species that is almost never true. The commonly used indices and the naïve diversity profile both ranked the springs as least diverse and tufa barriers as most diverse. The non-naïve diversity profiles based on similarity matrices (using feeding behavior and stream zonation preferences of species), showed even greater differences between these habitats, while ranking stream habitats close together, regardless of their longitudinal position. We constructed the Climate Score index (CSI) in order to assess how diversity and species’ vulnerability project the community’s resistance and/or resilience to climate change. The CSI ranked the springs as most vulnerable, followed by all habitats longitudinally placed below them. We highlight the importance of integrating ecological information into biodiversity and vulnerability assessment of freshwater communities.

Highlights

Diversity measures have for decades been one of the most important variables for describing and discussing ecological communities or assemblages, and nowadays show even greater merit when examining problems in the age of a rapid extinction of insects [1]. Standard diversity measures such as species richness, Shannon diversity index [2]; Simpson diversity index [3] and Berger-Parker index [4] might each exhibit different projections of diversity from the same given data set. These varying projections are due to the fact that each diversity index considers rare and dominant species in different ways, i.e., each gives different significance to species abundance
A quantitative measure of these differences is given with the sensitivity parameter q. This parameter ranges from 0 to ∞, where 0 gives no significance to abundance and is the equivalent to species richness, and where ∞ only considers the abundance of dominant species and is equivalent to the Berger-Parker index
Our results suggest using the Shannon diversity index when possible, as it considers abundance, while being most sensitive to rare species

Summary

Introduction

Diversity measures have for decades been one of the most important variables for describing and discussing ecological communities or assemblages, and nowadays show even greater merit when examining problems in the age of a rapid extinction of insects [1]. Standard diversity measures such as species richness, Shannon diversity index [2]; Simpson diversity index [3] and Berger-Parker index [4] might each exhibit different projections of diversity from the same given data set. This parameter ranges from 0 to ∞, where 0 gives no significance to abundance and is the equivalent to species richness, and where ∞ only considers the abundance of dominant species and is equivalent to the Berger-Parker index.

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