What We’re Reading- Oct 7, 2016

(Mal)adaptation on an Invasive Species
Soapberry bugs (Jadera haematoloma) are adapted to feed on the nutrient dense seeds of faux persil (Cardiospermum corindum).  Following introduction of the invasive golden rain tree (Koelreuteria elegans), some populations of soapberry bugs shifted hosts to feed on the invasive, which is easier to eat but less nutritious.  Adaptation was observed based on beak length, growth rate, and juvenile mortality.  This study used the same methodology as a paper from 1988 to compare traits of insects feeding on the different hosts, then compared contemporary and historic results.  The author found that populations collected on the different hosts are more similar than in 1988 at multiple traits, providing evidence that soapberry bug populations are becoming more similar as gene flow from populations adapted to the invasive swamp out adaptations to the native host.

Genetics of Priority Effects
When we think about how communities of species assemble, does it matter if one species arrives to a new habitat first?  Or, will the same species be present in a stable community despite arrival order?  Some communities show evidence of priority effects, where the order of species arrival does impact composition, often excluding late arriving species from the community.  This paper evaluated gene expression in nectar yeast species added in different orders under nutrient limiting and abundant conditions.  The paper shows a high level of novel tandem gene duplication, especially for nitrogen metabolism and cellular transport genes.  This suggests that the genetic basis of the priority effect for the nectar yeast Metschnikowia reukaufii is related to having genes which can efficiently take up amino acids from the substrate, depleting resources for other species entering the community.

This paper raises interesting questions about the genetic basis of priority effects in other systems.  Specifically, which traits aid a species in outcompeting (i.e. behavioral traits such as aggressiveness), and have they evolved novel genes, alleles, or expression patterns compared to their competitors?


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