Biogeographical network analysis of plant species distribution in the Mediterranean region

Abstract

The delimitation of bioregions helps to understand historical and ecological drivers of species distribution. In this work, we performed a network analysis of the spatial distribution patterns of plants in south of France (Languedoc‐Roussillon and Provence‐Alpes‐Côte d'Azur) to analyze the biogeographical structure of the French Mediterranean flora at different scales. We used a network approach to identify and characterize biogeographical regions, based on a large database containing 2.5 million of geolocalized plant records corresponding to more than 3,500 plant species. This methodology is performed following five steps, from the biogeographical bipartite network construction to the identification of biogeographical regions under the form of spatial network communities, the analysis of their interactions, and the identification of clusters of plant species based on the species contribution to the biogeographical regions. First, we identified two sub‐networks that distinguish Mediterranean and temperate biota. Then, we separated eight statistically significant bioregions that present a complex spatial structure. Some of them are spatially well delimited and match with particular geological entities. On the other hand, fuzzy transitions arise between adjacent bioregions that share a common geological setting, but are spread along a climatic gradient. The proposed network approach illustrates the biogeographical structure of the flora in southern France and provides precise insights into the relationships between bioregions. This approach sheds light on ecological drivers shaping the distribution of Mediterranean biota: The interplay between a climatic gradient and geological substrate shapes biodiversity patterns. Finally, this work exemplifies why fragmented distributions are common in the Mediterranean region, isolating groups of species that share a similar eco‐evolutionary history.

Redefining floristic zones in the Korean Peninsula using high‐resolution georeferenced specimen data and self‐organizing maps

“…Across a broader area, there are also effects of climatic factors, such as latitude (Sanders, Lessard, Fitzpatrick, & Dunn, 2007). The sequential settlement, expansion, contraction, and maintenance of species with historical geographic environmental oscillations are major processes involving interactions between the biota and topographic locations in a given region; this has been reported in other ecological regions (Lenormand et al, 2019;Silva & Souza, 2018) (Gentili et al, 2015;Thomson, 2005) and the process of species differentiation.…”

“…Currently, approximately 30.3% of the southern part of the Korean Peninsula is urbanized or used for agriculture and 63.8% is occupied by forests, with other land covers accounting for the remaining 5.9% (Ministry of Land Infrastructure & Transport, 2016). For analysis, a grid system was overlaid on a national topographic map to combine the taxonomic groups located in each cell of the grid (cell size, 11.2 km × 13.9 km), with the location coordinates in a single data set (Graham & Hijmans, 2006;Lenormand et al, 2019).…”

“…The use of biota to investigate biogeographic regions, including their distribution patterns, is a key to better understand the ecological processes that create biotic differentiation and biodiversity at multiple spatiotemporal scales (Ricklefs, 2004). In particular, as an important step in understanding the spatial structure of biodiversity, delineating the distribution of these regions has been a foundation of basic and applied research in biogeography, ecology, earth science, and conservation ecology (Brum et al, 2017;Graham & Hijmans, 2006;Ibanez-Erquiaga, Pacheco, Rivadeneira, & Tejada, 2018;Kreft & Jetz, 2010;Lenormand et al, 2019;Olson et al, 2001;Ricklefs, 2004;Sun, Yan, & Xie, 2008). Until the late 20th century, the proposed biological regions were based on limited data, convenience, and expert opinions (White, 1983).…”

Ecological Niche Models Reveal Climate Change Effect on Biogeographical Regions: The Iberian Peninsula as a Case Study

“…The current biodiversity crisis has led to an increasing interest in biogeographical studies attempting to understand the spatial patterns of species distributions, boosted by technological advances such as geographical information systems and remote sensing [1][2][3][4][5]. Much effort has been dedicated to analyse how species are distributed across space, and how they are organised in regions of similar characteristics (e.g., [6,7]). These so-called biogeographical regions are ecologically and geographically defined areas of the Earth, generally with homogeneous geologic and environmental conditions [5,8,9].…”

Heterogeneous forest structures favor persistence of the grassland Mediterranean geophyte Gagea lacaitae

“…Since the late Holocene, climatic changes combined with human activities (deforestation and pastoralism intensification) have played a key role in expanding the surface of grasslands and reducing the area of Mediterranean deciduous forest (Jalut et al 2009;Quezel and Médail 2003). The south of France represents the north-western limit of the Mediterranean biome (Lenormand et al 2018). Many species reach their distribution limit as small isolated populations that are of high conservation value (Thompson 2005), most of them living in xeric grasslands (Papuga et al 2018).…”