Ecological niche features override biological traits and taxonomic relatedness as predictors of occupancy and abundance in lake littoral macroinvertebrates

Abstract

The degree to which species ecological and biological traits determine their distribution and abundance has intrigued ecologists for a long time, and it has seen a revival in recent years. This topic is important because it provides information about the determinants of species rarity and their conservation implications. We examined the effects of niche breadth, niche position, biological traits and taxonomic relatedness on the interspecific occupancy–abundance relationship, as well as on occupancy and abundance, in lake littoral macroinvertebrates. We sampled 48 lakes in a boreal lake district, found altogether 155 species, and calculated regional occupancy (as the proportion of sites occupied) and local abundance (as mean abundance at occupied sites) for each species. We determined niche position and niche breadth for each species using the outlying mean index analysis. Also, we calculated trait vectors and taxonomic vectors describing species trait similarity and taxonomic relatedness, respectively, using principal coordinates analysis. We found a strong positive occupancy–abundance relationship that was mostly explained by among‐species variation in niche position, followed by niche breadth. Instead, trait vectors and taxonomic vectors tended to be less important in affecting occupancy and abundance than the niche features. Our results strongly suggest that niche position, a measure of habitat availability for littoral macroinvertebrates, is the chief determinant of their occupancy and abundance. This finding has important implications for ecology and conservation of species, as species with marginal niche position, a reflection of low habitat availability, are both regionally rare and locally uncommon. Such species may face double jeopardy if environmental conditions change and affect their preferred marginal habitat types.

Using traits to explain interspecific variation in diatom occupancy and abundance across lakes and streams

“…Hydrological connectivity has indeed been shown to affect biodiversity through dispersal (Heino et al., ; Lopes et al., ). Overall, the positive relationship between occupancy and abundance for both lakes and streams is in line with earlier observations on various freshwater organism groups (Heino & Tolonen, ; Passy, ; Rocha et al., ; Verberk et al., ).…”

“…There were, however, subtle indications that species with taxonomic similarity may have rather similar levels of occupancy and abundance. Similar small effects of taxonomic aspects on occupancy and abundance of freshwater macroinvertebrates were found by Heino and Tolonen (). As biological traits and phylogenetic relatedness are partly linked to each other (Harvey, ), it is also possible that the small taxonomic effects we found may in fact reflect effects of biological traits other than those addressed here.…”

“…Species’ pH preferences were variably associated with occupancy in lakes and streams, but in general, different environmental preferences of species were not clearly related to their occupancy and abundance. This finding is partly contradictory to earlier studies showing that species’ ‘true’ niche parameters can greatly affect interspecific variation in occupancy and/or abundance of freshwater organisms (Heino & de Mendoza, ; Heino & Tolonen, ; Rocha et al., ; Tales et al., ; Verberk et al., ; Vilmi et al., ). The difference between these earlier investigations and our current study is that we used existing literature knowledge on species’ pH and trophic preferences, while ‘true’ niche parameters are calculated based on actually measured environmental variables.…”

“…When trying to reveal mechanisms behind the positive occupancy–abundance relationship, researchers have studied if and how species characteristics (e.g. biological traits, ecological preferences and phylogeny) are associated with variation in abundances and distributions of species (Heino & Tolonen, ; Passy, ; Rocha et al., ; Verberk, van Noordwijk, & Hildrew, ; Verberk et al., ; White, Ernest, Kerkhoff, & Enquist, ). The connections among species characteristics, abundances and distributions have traditionally been addressed using sites as data points and observing how these variables vary in space, that is, in a community ecology perspective (Heino & Tolonen, ; Verberk et al., ).…”

“…biological traits, ecological preferences and phylogeny) are associated with variation in abundances and distributions of species (Heino & Tolonen, ; Passy, ; Rocha et al., ; Verberk, van Noordwijk, & Hildrew, ; Verberk et al., ; White, Ernest, Kerkhoff, & Enquist, ). The connections among species characteristics, abundances and distributions have traditionally been addressed using sites as data points and observing how these variables vary in space, that is, in a community ecology perspective (Heino & Tolonen, ; Verberk et al., ). In recent years, novel attempts have been made to disentangle the roles of species characteristics on interspecific variation in occupancy and abundance (Heino & Tolonen, ; Rocha et al., ; Tales, Keith, & Oberdorff, ; Tonkin, Arimoro, & Haase, ).…”