Understanding dispersal limitation through the assessment of diversity patterns across phylogenetic scales below the species level

Abstract

Aim We show how macroecological patterns at different phylogenetic scales below the species level may aid the identification of the predominant process controlling biological assemblages (niche versus dispersal). We compare two taxa with different ecological and dispersal requirements (terrestrial molluscs and leaf beetles) in the same geographical setting. Location Iberian Peninsula. Time period 2010–2015. Major taxa Terrestrial molluscs and leaf beetles. Methods The cox1‐5′ fragment was sequenced for 1,592 mollusc specimens in 20 localities. Leaf beetle assemblages had been sequenced previously in 15 of these localities. Species richness, distance decay of similarity, endemism and range size were measured at two levels: molecular variants (i.e., haplotypes) and putative species (i.e., operational taxonomic units). Using a multi‐hierarchical macroecology approach, distance‐decay patterns were measured at multiple intermediate genealogical levels (nested clades) to assess whether the geometry of the ranges of lineages followed a fractal pattern. Results Richness and distance‐decay patterns at both molecular variant and species levels were different in leaf beetles and terrestrial molluscs, although both taxa showed a fractal pattern in the distance decay of similarity across genealogical levels. The self‐similarity of the distance‐decay pattern across phylogenetic scales suggests a predominance of neutral, but limited, dispersal driving macroecological patterns in both taxa. Endemism was similar in both taxa at the level of molecular variants but higher at the species level in terrestrial molluscs, and range size was smaller at both levels in terrestrial molluscs. Taken altogether, our results suggest that dispersal limitation is stronger in terrestrial molluscs. Main conclusion The assessment of how diversity patterns change at different phylogenetic scales below the species level allowed us to identify unifying characteristics in otherwise seemingly heterogeneous biological systems. Congruence was observed in diversity patterns of leaf beetles and terrestrial molluscs, suggesting that dispersal is a relevant process in both taxa but acts at a different strength.

The limited spatial scale of dispersal in soil arthropods revealed with whole-community haplotype-level metabarcoding

“…The key observation from the multi-hierarchical analysis is the correlated distance decay at haplotype and species level. Self-similarity is expected to be eroded by selection on adaptive traits at the species level, but not at the (neutral) haplotype level (Baselga et al, 2015; Gómez-Rodríguez et al, 2018). As the data largely confirm the self-similarity of distance decay at haplotype and species level, this is interpreted to support the predominant role of dispersal limitation driving community assembly.…”

“…This confounds the correlation (self-similarity) of distance decay at the species and haplotype levels, each driven by different processes, and thus the joint analysis of communities at genetic and species levels provides a formal test to discern if a particular spatial pattern of community assemblage is predominantly driven by dispersal (i.e., neutral) or niche-based processes (Baselga et al, 2013, 2015). In addition, multi-hierarchical analyses may also describe the spatial scale at which dispersal constraints act, and the variation of scale among different taxonomic groups or habitats (Gómez-Rodríguez, Miller, Castillejo, Iglesias-Piñeiro, & Baselga, 2018; Múrria et al, 2017). This framework remains to be exploited with whole-community mitochondrial cMBC.…”

The limited spatial scale of dispersal in soil arthropods revealed with whole‐community haplotype‐level metabarcoding

“…The self-similarity of distance decay of communities at genetic and species levels therefore provides a formal test to discern whether a particular spatial pattern of community assemblage is predominantly driven by stochastic dispersal or niche-based processes, as the latter will not usually produce this correlation (Baselga et al, 2013(Baselga et al, , 2015. In addition, multihierarchical analyses may also describe the spatial scale at which dispersal constraints act, and the variation of scale among different taxonomic groups or habitats (Gómez-Rodríguez, Miller, Castillejo, Iglesias-Piñeiro, & Baselga, 2018;Múrria et al, 2017). This framework remains to be exploited with whole-community metabarcoding.…”

Revealing community assembly through barcoding: Mediterranean butterflies and dispersal variation

“…Large‐scale sampling of mtDNA sequences across multiple species and localities provides new opportunities to describe and understand repeatable patterns that may fuel new theories (Blanchet, Prunier, & De Kort, 2017). This is exemplified by aquatic water beetles sampled across Europe (Baselga et al., 2013), together with leaf beetles (Baselga, Gómez‐Rodríguez, & Vogler, 2015) and gastropods (Gómez‐Rodríguez, Miller, Castillejo, Iglesias‐Piñero, & Baselga, 2019) sampled across the Iberian Peninsula, and aquatic insects sampled across Panama (Múrria, Rugenski, Whiles, & Vogler, 2015). These studies all reveal a strong role for stochasticity in structuring communities, with neutral processes of dispersal, mutation and genetic drift playing an important role.…”

“…Species‐rich invertebrate groups are ideal for such an approach, which is reflected in multi‐taxa multi‐site mtDNA studies to date (e.g. Baselga et al., 2013, 2015; Craft et al., 2010; Gómez‐Rodríguez et al., 2019; Múrria et al., 2015; Papadopoulou et al., 2011; Salces‐Castellano et al., 2020; Scalercio et al., 2020). Together with advances in both (a) the generation of community‐level metabarcode data and (b) the recovery of reliable intraspecific sequence variation (Andújar et al, 2020; Elbrecht, Vamos, Steinke, & Leese, 2018; Turon, Antich, Palacín, Præbel, & Wangensteen, 2019), the logistical constraints for site‐based community barcoding are greatly reduced, even for species‐rich and hyperdiverse assemblages (Arribas, Andújar, Salces‐Castellano, Emerson, & Vogler, 2020).…”