Direct vs. indirect effects of whole-genome duplication on prezygotic isolation in Chamerion angustifolium: Implications for rapid speciation.

Premise Of The Study: The depiction of polyploid speciation as instantaneous implies that strong prezygotic and postzygotic isolation form as a direct result of whole-genome duplication. However, the direct vs. indirect contributions of genome duplication to phenotypic divergence and prezygotic isolation are rarely quantified across multiple reproductive barriers.

Cytotype coexistence leads to triploid hybrid production in a diploid-tetraploid contact zone of Chamerion angustifolium (Onagraceae).

Premise Of The Study: Polyploids are often geographically segregated from their diploid progenitors, but the extent of sympatry and the consequences for reproductive isolation and coexistence are rarely quantified. •

Methods: In this study, we document the distribution and co-occurrence of diploid and tetraploid Chamerion angustifolium among 57 populations within the diploid-tetraploid contact zone in the Canadian Rocky Mountains. Rates of hybrid mating in mixed-ploidy populations were inferred from the frequency of triploid offspring in open-pollinated seed families.

Pollinator-mediated assortative mating in mixed ploidy populations of Chamerion angustifolium (Onagraceae).

Establishment of polyploid individuals within diploid populations is theoretically unlikely unless polyploids are reproductively isolated, pre-zygotically, through assortative pollination. Here, we quantify the contribution of pollinator diversity and foraging behaviour to assortative pollen deposition in three mixed-ploidy populations of Chamerion angustifolium (Onagraceae). Diploids and tetraploids were not differentiated with respect to composition of insect visitors.

Reproductive isolation between autotetraploids and their diploid progenitors in fireweed, Chamerion angustifolium (Onagraceae).

Polyploidy is viewed as an important mechanism of sympatric speciation, but few studies have documented the reproductive barriers between polyploids and their diploid progenitors or explored the significance of assortative mating for polyploid establishment. Here we synthesize new and existing data on five prezygotic (geographic isolation, flowering asynchrony, pollinator fidelity, self-pollination, gametic selection) and two postzygotic (selection against triploid hybrids, inbreeding depression) reproductive barriers between diploid and autotetraploid individuals of the perennial plant Chamerion angustifolium. We also present estimates of realized rates of between-ploidy mating and examine the impact of assortative mating on polyploid dynamics using computer simulation.

Managing honey bees (Hymenoptera: Apidae) for greenhouse tomato pollination.

Although commercially reared colonies of bumble bees (Bombus sp.) are the primary pollinator world-wide for greenhouse tomatoes (Lycopersicon esculentum Mill.) previous research indicates that honey bees (Apis mellifera L.