Learning the Hard Way: Imprinting Can Enhance Enforced Shifts in Habitat Choice

Abstract

We investigated the potential importance of learning in habitat choice within a young hybrid zone of two closely related species of birds. Pied flycatchers (Ficedula hypoleuca) are being excluded from deciduous habitats into a mixed forest type by collared flycatchers (F. albicollis). We investigated whether this enforced habitat shift influenced reproductive isolation between the two species, and, by cross-fostering nestlings, we tested whether learning may lead to a corresponding shift in habitat choice in consecutive generations. Our results show that the majority of the recruits, even if translocated across different habitat types, return to breed in the area where they were fostered. As male pied flycatchers were more likely to hybridize in the originally preferred habitat, we argue that early imprinting on an alternate habitat can play an important role in increasing reproductive isolation and facilitate regional coexistence between species experiencing secondary contact.

Asymmetric dominance and asymmetric mate choice oppose premating isolation after allopatric divergence

“…2009). In contrast to the above examples, asymmetries in competitive abilities can also launch processes which promote assortative mating, for example when asymmetric dominance relationships between taxa underlie their segregation into different habitats (Vallin and Qvarnström 2011; Vallin et al., 2012b; Winkelmann et al. 2014).…”

“…2012). In resource-based breeding systems, for instance, interspecific competition can on the one hand lead to habitat segregation and hence strengthen premating isolation (Vallin and Qvarnström 2011), but can on the other hand interfere with assortative mating by constraining the choice of conspecific males. The latter situation arises when the outcome of male–male competition determines the availability of potential mates.…”

Interspecific competition promotes habitat and morphological divergence in a secondary contact zone between two hybridizing songbirds

“…However, spatial segregation of the nightingale species alone could significantly reduce the likelihood of heterospecific mating in sympatry and thus enhance the prezygotic isolation. Habitat imprinting can then further strengthen the barrier as has been observed in Ficedula flycatchers (Vallin & Qvarnström, ). In addition, ecological differentiation may increase the degree of extrinsic postzygotic isolation as hybrids with intermediate morphology and ecological requirements may be exposed to higher competition from both parental species.…”

Parallel Ecological Speciation in Plants?

“…We view systems with apparent immigrant or hybrid inviability (e.g., serpentine adaptation), long-term persistence of divergent populations in sympatry, or strong divergence in mating system as indirect evidence that barriers likely exist. Although we would not consider isolation that has no genetic basis as evidence for parallel ecological speciation, we acknowledge that phenotypic plasticity can facilitate or impede the evolution of reproductive barriers and is an important consideration for studies of ecological speciation [43] (e.g., [44]). Furthermore, because explicitly testing that isolation is genetically based was rare in our candidate studies, we only required the genetic basis of isolation to be confirmed for cases to have strong direct evidence.…”