Taxonomic, functional and phylogenetic metacommunity ecology of cladoceran zooplankton along urbanization gradients

Abstract

As human population size increases and cities become denser, several urban-related selection pressures increasingly affect species composition in both terrestrial and aquatic habitats. Yet, it is not well known whether and how urbanization influences other facets of biodiversity, such as the functional and evolutionary composition of communities, and at what spatial scale urbanization acts. Here we used a hierarchical sampling design in which urbanization levels were quantified at seven spatial scales (ranging from 50 to 3200 m radii). We found that urbanization gradients are associated with a strong shift in cladoceran zooplankton species traits, which in turn affected phylogenetic composition of the entire metacommunity, but only when considering urbanization at the smallest spatial scale (50 m radius). Specifically, small cladoceran species dominated in more urbanized ponds whereas large-bodied, strong competitors prevailed in less urbanized systems. We also show that trait and phylogenetic metrics strongly increase the amount of variation in b-diversity that can be explained by degree of urbanization, environmental and spatial factors. This suggests that the mechanisms shaping b-diversity in our study system are mediated by traits and phylogenetic relatedness rather than species identities. Our study indicates that accounting for traits and phylogeny in metacommunity analyses helps to explain seemingly idiosyncratic patterns of variation in zooplankton species composition along urbanization gradients. The fact that urbanization acts only at the smallest spatial scale suggests that correctly managing environmental conditions locally has the power to counteract the effects of urbanization on biodiversity patterns. The multidimensional approach we applied here can be applied to other systems and organism groups and seems to be key in understanding how overall biodiversity changes in response to anthropogenic pressures and how this scales up to affect ecosystem functioning.

City life on fast lanes: Urbanization induces an evolutionary shift towards a faster lifestyle in the water flea Daphnia

“…While our observation of a shift in pace‐of‐life shift linked to urbanization is in general correspondence with expectations under a scenario of adaptive evolution in response to the urban heat island effect, we do not preclude that other stressors linked to urbanization may equally have impacted this shift. A survey of local environmental conditions in a set of 83 ponds (Jessie Engelen, Caroline Souffreau and others, unpublished data; see also Gianuca et al., ) did not reveal strong and systematic differences in nutrient concentrations (eutrophication), salt pollution, pesticide load and metal contamination along the urbanization gradient. Yet, our observation of a change in pace of life might reflect adaptation to a higher incidence of mechanical and hydrological disturbances (e.g., pond management: clearance of the litter layer, addition and removal of water) or extreme temperatures that are likely more prominent in urban compared to rural ponds (Wouters et al., ; Brans et al., ; K. I. Brans, personal observations).…”

Review: Toward management of urban ponds for freshwater biodiversity

“…For Cladocera (zooplankton), smaller species were more diverse in more urbanized ponds in contrast to larger‐bodied species, which were more diverse in less urbanized systems (Gianuca et al. ). Macroinvertebrate taxa tolerant of environmental pressures can also dominate in urban ponds, and this is the case with Oligochaeta or Chironomidae, which are often very numerous in terms of both abundance and species richness (Bishop et al.…”

“…For example, the smallest radius (50 m) had the greatest impact on the zooplankton community in urban ponds in Belgium, among 7 radii investigated up to 3.2 km (Gianuca et al. ). Much larger radii (800 m–1.8 km) were found to influence vegetation and benthic macroinvertebrate assemblages in urban ponds in Ottawa (Patenaude et al.…”

Environmental heterogeneity and dispersal limitation explain different aspects of β‐diversity in Neotropical fish assemblages

“…Hence, there is evidence showing that spatial factors and stochasticity (e.g. stochastic extinctions, drift, priority effects) may be more important at the taxonomic level, whereas environment has stronger effects on the variation of assemblages' functional composition (Fukami, Martijn Bezemer, Mortimer, & Putten, ; Gianuca, Declerck, Lemmens, & De Meester, ; Gianuca, Engelen, et al., ).…”

“…Therefore, we aimed to test two main ideas about factors structuring fish assemblages in mainstem and tributary sites of a Neotropical river system. First, whether spatial factors and environment explained different aspects of β‐diversity (Fukami et al., ; Gianuca, Declerck, et al., ; Gianuca, Engelen, et al., ; Leibold & Chase, ). Thus, we expected a higher portion of variance in functional dissimilarity to be explained by environmental factors, and spatial factors to explain in a higher degree the species dissimilarity among habitats.…”