caa a22 4500 445857781 CHVBK 20180317145433.0 cr unu---uuuuu 170323e20110801xx s 000 0 eng 10.1007/s10592-011-0211-3 doi (NATIONALLICENCE)springer-10.1007/s10592-011-0211-3 Genetic monitoring of two decades of hybridization between allis shad ( Alosa alosa ) and twaite shad ( Alosa fallax ) [Elektronische Daten] [M. Jolly, P. Maitland, M. Genner] Habitat alteration has been implicated in driving hybridization between the sympatric migratory shads Alosa alosa and Alosa fallax. Morphological and molecular evidence is consistent with hybridization across the overlapping range of these species, but the temporal extent of hybrid occurrence and genetic consequences for populations have not been explored. Using eight nuclear microsatellite loci and samples collected between 1989 and 2008 in the Solway Firth (UK), we genetically identified hybrids, studied temporal changes in their frequency, and explored changes in allele frequencies of parental populations. These molecular data confirmed the hybrid status of individuals identified using morphology (number of rakers on the outer gill arch), and enabled separation of hybrids from purebred individuals. Mitochondrial cytochrome-b sequencing revealed the presence of two haplogroups, each predominantly occurring in one species. Heterospecific haplotypes were found in 22.3 and 12.8% of A. alosa and A. fallax individuals, respectively, consistent with backcrossing and suggesting that hybrids are fertile. On average, microsatellite-identified hybrids comprised 12.7% of all samples, but when individuals with cytonuclear discordance were also considered introgressed on average 25.4% of individuals were of hybrid ancestry. Overall, allelic richness remained largely unchanged within species, but there were declines in the inbreeding coefficient (F IS) of both species and episodes of significant temporal allelic frequency change. Hybrids sampled between 2004 and 2008 showed no evidence of lower fecundity relative to purebred individuals. Together, results suggest that hybridization between shad species in northern Europe is prevalent, and has been ongoing over at least two decades. The challenge is now to understand the extent to which observed patterns are linked to immigration from other populations, and the mechanisms that have prevented species collapse despite apparent hybrid fertility and longstanding introgression of neutral markers. Springer Science+Business Media B.V., 2011 Alosa nationallicence Hybridization nationallicence Introgression nationallicence Temporal change nationallicence Selection nationallicence Jolly M. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, PL1 2PB, Plymouth, UK aut Maitland P. Fish Conservation Centre, Gladshot, EH41 4NR, Haddington, Scotland, UK aut Genner M. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, PL1 2PB, Plymouth, UK aut Conservation Genetics Springer Netherlands 12/4(2011-08-01), 1087-1100 1566-0621 12:4<1087 2011 12 10592 https://doi.org/10.1007/s10592-011-0211-3 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10592-011-0211-3 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Jolly M. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, PL1 2PB, Plymouth, UK aut NATIONALLICENCE 700 1- Maitland P. Fish Conservation Centre, Gladshot, EH41 4NR, Haddington, Scotland, UK aut NATIONALLICENCE 700 1- Genner M. Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, PL1 2PB, Plymouth, UK aut NATIONALLICENCE 773 0- Conservation Genetics Springer Netherlands 12/4(2011-08-01), 1087-1100 1566-0621 12:4<1087 2011 12 10592 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer