The role of spatial environmental factors as determinants of large branchiopod distribution in Tunisian temporary ponds

Abstract

The influence of spatial and environmental factors in explaining the structure of large branchiopod assemblages at different spatial scales is still poorly explored. We hypothesized that the extent of actual spatial connectivity, and thus the spatial distribution of a metacommunity, may depend on the environmental conditions as represented by climatic gradients and the structural characteristics of the landscape. To test this hypothesis, the distributional patterns of 14 large branchiopod species in a set of 177 temporary water bodies repeatedly sampled across Tunisia and on its main islands were analysed. Physical, chemical, morphological and climatic characteristics of the studied water bodies were collected as well, and spatial structures were described using distance-based Moran’s Eigenvector Maps. Distance-based Redundancy Analysis and variance partitioning explained more than one-half of total variation. Mantel’s autocorrelograms demonstrated that species composition was spatially autocorrelated at shorter distances in the Mediterranean part of the country than in the southern, more arid part. These results suggest that both dispersal limitation and species response to spatially structured environmental gradients might be involved in determining large branchiopod distribution in Tunisia and that these patterns may greatly vary on a regional basis

Updated checklist and distribution of large branchiopods (Branchiopoda: Anostraca, Notostraca, Spinicaudata) in Tunisia

“…The importance of the isohyets of 300 and 500 mm y -1 in determining different crustacean assemblages in the Maghreb has been widely accepted and implemented, e.g. by Dumont et al (1979), Thiéry (1991), Turki and El Abed (1999), Samraoui and Dumont (2002), and Stoch et al (2016).…”

“…Based on the available data, it is possible to differentiate four major ecological groups within the Tunisian large branchiopods (see Stoch et al 2016 for a discussion). These show, in fact, quite a sharp latitudinal gradient, with some species being confined to the more arid areas of Tunisia that are located in the southern and central portion of the country (i.e., Tanymastigites perrieri, Triops granarius and Leptestheria mayeti), whereas others are strictly linked to the more humid areas of northern Tunisia (i.e., Chirocephalus diaphanus and Lepidurus apus lubbocki).…”

“…In this paper, the most updated information on the presence and distribution of large branchiopods in Tunisian temporary ponds is reported, whereas an analysis of the ecological factors affecting their distribution has been published in Stoch et al (2016).…”

New challenges in anostracan research: old issues, new perspectives and hot topics

“…Although it is widely accepted that different spatial and temporal scales govern species distribution and their coexistence in natural environments (e.g., Stoch et al, 2016;Marrone et al, 2017a), the discussion about biogeographical patterns in organisms subjected to passive dispersal is still open. As regards anostracans, dispersal is more clearly understood regarding mechanisms (reviewed in Rogers, 2014), although dispersal patterns are more stochastic (Daniels, et al, 2004;Rogers, 2015).…”

“…Since then, the discovery and description of several new taxa, and revisions of some existing ones, brought to us an updated checklist of more than 350 extant species in 10 families (Rogers, 2013), but more work is needed. In fact, as stressed by Brendonck et al (2008), Anostraca is among the least known taxonomic groups in inland waters and, although some data are available on large-scale distributions of species and higher taxa (e.g., Brtek & Thiéry, 1995;Brtek & Mura, 2000;Brendonck et al, 2008;Stoch et al, 2016), we are still far from a clear understanding of the phylogeny, ecology and biogeography of the order, probably due to the fact that they mainly inhabit temporary ponds, a poorly studied ecosystems (e.g., Bagella et al, 2016). This paper summarizes the outcomes of a call we launched about 1 year ago among scientists working on Anostraca to commemorate Professor Graziella Mura, a pioneer of modern studies on this group of animals, who had recently passed away (Marrone et al, 2017b).…”