While gene flow between these populations may not currently be ongoing, their shared mitochondrial haplotype suggests recent hydrogeological connections and/or dispersal across contemporary barriers.
Some of these lineages appear to be maintained in the absence of contemporary barriers to gene flow, possibly by differences in reproductive timing or pelage-based assortative mating, suggesting that populations usually recognized as subspecies have a long history of reproductive isolation.
Importantly, there is no obvious contemporary barrier between the extant clades of E. ockendeni, such as a major river as would be suggested by the river barrier hypothesis [ 13- 16]).
"Pearl" was written, of course, for a specific audience, and some of its symbols and techniques have become, for contemporary readers, barriers to understanding.
Phylogeographical breaks and contemporary oceanographic barriers (or biogeographical transition zones) are often mismatched in marine restricted dispersers [ 33].
Migration may be particularly depressed there due to the presence of contemporary oceanographic barriers to dispersal, or be as low as elsewhere and simply reflect the inherent low vagility of the species.
This together with the Yangtze River discharge is assumed to form a contemporary dispersal barrier for marine species that require a hard substratum (e.g. intertidal rocky shore) or with larvae that cannot tolerant decreased salinity, including the gastropod Cellana toreuma [ 20], the bivalve Cyclina sinensis [ 34] and the macroalga Sargassum hemiphyllum [ 18, 35].
From founding the KidsVote Initiative in Holyoke, MA to participating in a delegation to Puerto Rico of academics and community leaders in exploring contemporary and historical barriers to economic mobility of Puerto Ricans in Holyoke, Amaad has been deeply involved in the community.
In contrast, the pattern of mtDNA evolution closely reflected contemporary and historical marine barriers.
Kinship networks, for example, are typically not the first port of call for solutions to contemporary rights violations or barriers.
Some conservation scientists have promoted the intentional transport of species beyond their current ranges, as they fear that the low dispersal abilities of many species and the numerous dispersal barriers in contemporary landscapes may prevent species from naturally tracking changing climate, which has inspired intense debate among scientists and policy makers (McLachlan et al. 2007).
