The macroecology of rapid evolutionary radiation

Abstract

A long-standing debate in ecology addresses whether community composition is the result of stochastic factors or assembly rules. Non-random, over-dispersed patterns of species co-occurrence have commonly been attributed to competition-a particularly important force in adaptive radiation. We thus examined the macroecology of the recently radiated cichlid rock-fish assemblage in Lake Malawi, Africa at a spectrum of increasingly fine spatial scales (entire lake to depth within rock-reef sites). Along this range of spatial scales, we observed a signal of community structure (decreased co-occurrence of species) at the largest and smallest scales, but not in between. Evidence suggests that the lakewide signature of structure is driven by extreme endemism and micro-allopatric speciation, while patterns of reduced co-occurrence with depth are indicative of species interactions. We identified a 'core' set of rock-reef species, found in combination throughout the lake, whose depth profiles exhibited replicated positive and negative correlation. Our results provide insight into how ecological communities may be structured differently at distinct spatial scales, re-emphasize the importance of local species interactions in community assembly, and further elucidate the processes shaping speciation in this model adaptive radiation.

Composition, richness and nonrandom assembly of culturable bacterial-microfungal communities in floral nectar of Mediterranean plants

“…Nonrandom co-occurrence patterns between taxa may indicate that deterministic processes are important in structuring communities but, by themselves, do not identify the causal mechanisms accounting for such patterning (Horner-Devine et al, 2007). Low co-occurrence is usually interpreted as evidence of divergence in habitat preference, differences in growth constraints between taxa, and/or negative interactions (Gotelli & McCabe, 2002;Horner-Devine et al, 2007;Pan & May, 2009;Eiler et al, 2011;Parnell & Streelman, 2011). Oppositely, positive species co-occurrences are usually attributed to different species having similar environmental requirements and not showing competitive exclusion, and/or positive species interactions (Horner-Devine et al, 2007;Pan & May, 2009;Eiler et al, 2011;Parnell & Streelman, 2011).…”

“…Low co-occurrence is usually interpreted as evidence of divergence in habitat preference, differences in growth constraints between taxa, and/or negative interactions (Gotelli & McCabe, 2002;Horner-Devine et al, 2007;Pan & May, 2009;Eiler et al, 2011;Parnell & Streelman, 2011). Oppositely, positive species co-occurrences are usually attributed to different species having similar environmental requirements and not showing competitive exclusion, and/or positive species interactions (Horner-Devine et al, 2007;Pan & May, 2009;Eiler et al, 2011;Parnell & Streelman, 2011). Furthermore, in the case of nectar microorganisms, positive co-occurrence might be the result of flower colonisation via the same dispersal vectors, mainly flower-visiting insects (Pozo et al, 2012).…”

Integrated Brain Diversification along the Early Neuraxes

“…Within Lake Malawi, members of the rock-dwelling (locally called 'mbuna') versus sand-dwelling (locally, 'utaka') evolutionary lineages share similar genomes [Loh et al, 2008] but exhibit distinct brains and behaviors [van Staaden et al, 1994;Huber et al, 1997]. Mbuna are strongly territorial [Parnell and Streelman, 2011]; they breed and feed at a high density in complex 3-D habitats. Most mbuna eat algae from the substratum.…”

Genetic interactions controlling sex and color establish the potential for sexual conflict in Lake Malawi cichlid fishes

“…The rapidity of this radiation, extreme endemism (Parnell and Streelman, 2011) and continued low levels of gene flow between species (Mims et al, 2010) has led to a phenomenon wherein genetic incompatibilities between lineages are considerably outpaced by speciation (Stelkens et al, 2010). The integrity of species is maintained by pre-zygotic mechanismsassortative mating based on visual (Seehausen et al, 1997(Seehausen et al, , 2008van Oppen et al, 1998;Knight and Turner, 2004;Maan et al, 2004;Carleton, 2009), auditory (Amorim et al, 2004Simoes et al, 2008;Smith and van Staaden, 2009;Danley et al, 2011) and olfactory cues (Jordan et al, 2003;Plenderleith et al, 2005;Cole and Stacey, 2006) that sometimes breakdown.…”