A synthetic phylogeny of freshwater crayfish: insights for conservation

Abstract

Phylogenetic systematics is heading for a renaissance where we shift from considering our phylogenetic estimates as a static image in a published paper and taxonomies as a hardcopy checklist to treating both the phylogenetic estimate and dynamic taxonomies as metadata for further analyses. The Open Tree of Life project ( opentreeoflife.org ) is developing synthesis tools for harnessing the power of phylogenetic inference and robust taxonomy to develop a synthetic tree of life. We capitalize on this approach to estimate a synthesis tree for the freshwater crayfish. The crayfish make an exceptional group to demonstrate the utility of the synthesis approach, as there recently have been a number of phylogenetic studies on the crayfishes along with a robust underlying taxonomic framework. Importantly, the crayfish have also been extensively assessed by an IUCN Red List team and therefore have accurate and up-to-date area and conservation status data available for analysis within a phylogenetic context. Here, we develop a synthesis phylogeny for the world's freshwater crayfish and examine the phylogenetic distribution of threat. We also estimate a molecular phylogeny based on all available GenBank crayfish sequences and use this tree to estimate divergence times and test for divergence rate variation. Finally, we conduct EDGE and HEDGE analyses and identify a number of species of freshwater crayfish of highest priority in conservation efforts.

Mitochondrial cytochrome oxidase I gene analysis indicates a restricted genetic background in Finnish noble crayfish(Astacus astacus)stocks

“…The present study represents a large dataset from noble crayfish mitochondrial COI-gene, which is one of the five most commonly used coregenes employed to evaluate the diversity of crustacean species (Bybee et al, 2011;Owen et al, 2015). The results obtained in this study show, that the genetic variation in the northernmost distribution area of noble crayfish is either severely diminished, or never even existed.…”

The marbled crayfish (Decapoda: Cambaridae) represents an independent new species

“…Genetic analysis can be used to reveal independent species in the absence of distinctive morphological features (Bickford et al, 2007). Furthermore, convergent evolution of morphological characters appears to be common in cambarids (Breinholt et al, 2012), which further illustrates the value of genetic information for crayfish taxonomy (Owen et al, 2015). Complete mitochondrial genome sequencing of marbled crayfish from diverse sources revealed their genetic homogeneity and strongly suggested a single origin of the known marbled crayfish population (Vogt et al, 2015).…”

Australian spiny mountain crayfish and their temnocephalan ectosymbionts: an ancient association on the edge of coextinction?

“…The more northerly crayfish (see also [46]) and their associated Temnosewellia species exhibit greater ED owing to their early divergence, comparative geographical isolation and, correspondingly, high genetic distinctiveness. In addition, the geographical ranges of northerly Euastacus species (and their temnocephalans) tend to be smaller than those of southern species and lie at higher altitudes (see also qualitative discussion in [33]).…”

“…In addition, the geographical ranges of northerly Euastacus species (and their temnocephalans) tend to be smaller than those of southern species and lie at higher altitudes (see also qualitative discussion in [33]). A recent study estimating EDGE scores across a large sample (60%) of global freshwater crayfish species found extremely high values for Euastacus species, with several (including the northernmost, E. robertsi) within the 10 highest estimated EDGE scores [46]. Geographical range size is an important predictor of extinction risk [59] and a key variable in conservation assessment [60], which may in turn be used to calculate combined metrics of distinctiveness and extinction risk such as EDGE and phylogenetic endemism [61].…”

“…For each crayfish species, we also calculated the evolutionarily distinct and globally endangered (EDGE) score [44], which weights ED by probability of extinction. Input extinction probabilities were based on the assessed IUCN Red List conservation status (least concern ¼ 0.025, near threatened ¼ 0.05, vulnerable ¼ 0.1, endangered ¼ 0.2, critically endangered ¼ 0.4) following [44,46].…”