transparent gif


Ej inloggad.

Göteborgs universitets publikationer

The maintenance of a cline in the marine snail Littorina saxatilis: The role of home site advantage and hybrid fitness

Författare och institution:
E. Rolan-Alvarez (-); Kerstin Johannesson (Institutionen för marin ekologi & Institutionen för marin ekologi, Tjärnö marinbiologiska laboratorium); Johan Erlandsson (Institutionen för marin ekologi & Institutionen för marin ekologi, Tjärnö marinbiologiska laboratorium)
Publicerad i:
Evolution, 51 ( 6 ) s. 1838-1847
Artikel, refereegranskad vetenskaplig
Sammanfattning (abstract):
Steep clinal transitions in one or several inherited characters between genetically distinct populations are usually referred to as hybrid zones. Essentially two different mechanisms may maintain strap genetic dines. Either selection acts against hybrids that are unfit over the entire zone due to their mixed genetic origin (endogenous selection), or hybrids and parental types attain different fitness values in different parts of the dine (exogenous selection). Survival rate estimates of hybrids and parental forms in different regions of the dine may be used to distinguish between these models to assess how the dine is maintained. We used reciprocal transplants to test the relative survival rates of two parental ecotypes and their hybrids over microscale hybrid zones in the direct-developing marine snail Littorina saxatilis (Olivi) on the rocky shores of Galicia, Spain. One of the parental forms occupies upper and the other lower shores, and the hybrids are found at various proportions (1-38%) along with both parental forms in a midshore zone a few meters wide. The survival rate over one month was 39-52% of the native ecotype on upper shores, but only 2-8% for the lower-shore ecotype. In contrast, only 4-8% of the upper-shore ecotype but 53% of large (> 6 mm) and 8% of small (3-6 mm) native lower-shore ecotype survived in the lower shores. In the midshores, both the two parental ecotypes and the hybrids survived about equally well. Thus there is a considerable advantage for the native ecotypes in the upper and lower shores, while in the hybrid zone none of the morphs. hybrids included, are favored. This indicates that the dimorphism of L. saxatilis is maintained by steep cross-shore selection gradients, thus supporting the selection-gradient model of hybrid zones. We performed field and laboratory experiments that suggest physical factors and predation as important selective agents. Earlier studies indicate assortative mating between the two ecotypes in the midshore. This is unexpected in a hybrid zone maintained by selection gradients, and it seems as if the reproductive barrier compresses the hybrid zone considerably.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
Biologiska vetenskaper
Biologiska vetenskaper ->
differential selection, hybrid zone, reciprocal transplants, reinforcement, selection-gradient model, tension-zone model, viability estimates, 2 sympatric morphs, intertidal snail, nucella-lapillus, heterogeneous environments, genetic differentiation, protected shores, shell morphology, sexual selection, size, gastropod
Postens nummer:
Posten skapad:
2009-01-01 17:15
Posten ändrad:
2010-01-26 10:51

Visa i Endnote-format

Göteborgs universitet • Tel. 031-786 0000
© Göteborgs universitet 2007