Microplate tectonics and environmental factors as distribution drivers in Western Mediterranean freshwater planarians

Abstract

Aim Species biogeography mainly focuses on palaeogeographical events, while environmental factors are generally overlooked despite their importance in species diversification. Here, we use an integrative approach to understand how palaeogeographical and environmental processes shape species distribution and focus on freshwater planarians as the model system. Location Western Mediterranean. Taxon Dugesia. Methods We inferred the phylogenetic relationships of most known Dugesia species in the area using six molecular markers. We then estimated their divergence times and reconstructed their ancestral distribution ranges. We also performed environmental niche modelling analyses using Dugesia subtentaculata as a model to evaluate the effects of several hydro‐environmental variables and the likely existence of interspecific competition on Dugesia distributions. Results Our results provide a new phylogenetic scheme for Dugesia from the Western Mediterranean and show that the time splits between the lineages and their putative ancestral distribution ranges are correlated with microplate tectonic dynamics within the region during the Oligocene–Miocene period. Our environmental niche modelling analyses indicate that the type of land cover and the slope of the terrain are the most important abiotic factors driving the distribution of Dugesia from this region. Finally, we found a partial niche overlap between D. subtentaculata and two other common planarian species from the Iberian Peninsula. Main conclusions The microplate tectonic dynamics of the Western Mediterranean during the Oligocene–Miocene period, together with the position of the mountain ranges and posterior climate changes, may have played crucial roles in driving the biogeographical history of Dugesia in this region. Moreover, both interspecific competition and changes in fluvial characteristics driven by human activities may affect the current diversity and distribution of Dugesia in the Western Mediterranean. This study highlights the importance of integrating different types of information to study the biogeographical history of a species.

Niche modelling and molecular phylogenetics unravel the invasion biology and worldwide colonization of three species of the freshwater planarian genus Girardia (Platyhelminthes, Tricladida)

“…3). The importance of this variable has been reported also for many other introduced plant and animal species (Johnston et In that respect, it is noteworthy that the factor "tolerance for anthropogenic habitats" played no role in the explanation of the autochthonous distribution of D. subtentaculata in the Iberian Peninsula (Leria et al 2022). Anthropogenic habitats generally are characterised by low autochthonous species diversity, thus offering empty niches for invasive species that can use these as a springboard to natural habitats (Dietz and Edwards 2006).…”

“…A case of wide physiological tolerance concerns temperature, with the three Girardia species presenting a range of highly suitable temperatures that is much broader than in other freshwater planarian species (Vila-Farré and Rink 2018; Leria et al 2022). For example, Polycelis felina exhibits an optimality maximum at 4ºC, with the optimality rapidly decreasing at temperatures above 10ºC, while Dugesia subtentaculata shows a narrow temperature range between 12 o and 15ºC with a high suitability (Leria et al 2022). In contrast, in Girardia high suitability was found for temperatures ranging from around 4ºC to roughly 20ºC.…”

“…Six hydro-environmental variables were downloaded from the RiverATLAS database (Linke et al 2019), at a spatial resolution of either 15 or 30 arc-seconds, for the variables Temperature, Natural Discharge, Precipitation, Land Cover Classes, Lithological Classes, and Slope. In a recent study on planarians of the genus Dugesia Girard, 1850 from the Western Mediterranean region it was shown that these variables are not correlated (Leria et al 2022). Future potential distribution of these three Girardia species was inferred under two different scenarios of climate change.…”

“…and with G. dorotocephala (recently identi ed by DNA barcoding in our laboratory). Moreover, optimal environmental conditions for D. subtentaculata were recently estimated in a niche modeling analysis (Leria et al 2022). For this species optimal conditions are present along the northern and western coasts of the Iberian Peninsula, a region with principally deciduous tree cover, an annual average temperature around 14ºC, and relatively high precipitation regimes.…”

Niche modelling and molecular phylogenetics unravel the colonisation biology of three species of the freshwater planarian genus Girardia (Platyhelminthes, Tricladida)

“…Six hydro-environmental variables were downloaded from the RiverATLAS database (Linke et al 2019), at a spatial resolution of either 15 or 30 arc-seconds, for the variables Temperature, Natural Discharge, Precipitation, Land Cover Classes, Lithological Classes, and Slope. These variables were speci cally chosen because they had already been shown to be informative (and non-correlated to each other) and to predict the potential distribution of freshwater planarians (Leria et al 2022). Future potential distribution of these three Girardia species was inferred under two different scenarios of climate change.…”