title for learn-about sections for chitons in A SNAIL'S ODYSSEY
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Genetic patterns

  Topics of interest in the ecology of chitons include genetic patterns, considered here, and HABITAT PREFERENCES & ROLE AS HERBIVORES, COMPETITIVE INTERACTIONS, and ORIENTATION & HOMING, considered in other sections.
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Research study 1

Chitons are lecithotrophic and have a relatively short larval life, so their dissemination potentials should be relatively restricted.  How does this affect the genetic makeup of a population or a species through its north-south distribution?  This is examined by researchers from Columbia University, New York and California State University, Fullerton who collect specimens of 28 species of chitons from 130 populations/locations from Alaska to the Gulf of California.  Results show a strong trend between gene flow and latitude; namely, species living at lower latitudes tend to have more genetically isolated populations.  The authors speculate that lower seawater temperatures at higher latitudes lead to longer duration larval lifespans and, thus, greater genetic “connectivity” – equating to more genetic homogeneity in more northern populations.  In contrast, the shorter larval durations of low-latitude species lead to smaller dispersal potentials, promoting increased genetic divergence and the potential for greater speciation.  The paper provides a unique broader-than-normal-scale insight into the population genetics and phylogeography of a single taxonomic group, linking possible environmental cause to observed genetic divergence. Kelly & Eernisse 2007 Evolution (March): 700.

NOTE  larvae are non-feeding, relying instead on yolk stores provided by the parent.  The authors note that some of the species may actually lay benthic egg masses, but this is not known for sure

NOTE  analysis of cytochrome c oxidase subunit I mtDNA locus

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Research study 2

map showing study locations on Vancouver Island, B.C. for investigation of genetics of black-leather chitons Katharina tunicataA later paper by researchers from Queen’s University Belfast examines the same topic in closer geographic scale for black-leather chitons Katharina tunicata.  Genetic analysis of individuals from 5 sites on Vancouver Island, British Columbia (see map) separated by 15-150km discloses no significant genetic differentiation.  This suggests a general absence of barriers to dispersal of larvae, thus leading to extensive small-scale gene flow. Results of analyses of past photograph of several black-leather chitons Katharina tunicatademographic patterns of K. tunicata suggest to the authors that the species  has already “weathered” previous periods of climate change associated with Pleistocene glaciations and thus seems well adapted to withstand current and future trends in global warming.  Doonan et al. 2012 Biol J Linn Soc 106: 589.

NOTE  nuclear single-nucleotide polymorphisms (SNPs) and  sequencing of mitochondrial DNA

Preference for mid-intertidal habitats where brown algae
Hedophyllum sessile are abundant meets 2 needs for black-
leather chitons: a moisture-retaining overstory and a favourite food