Patterns of floral colour neighbourhood and their effects on female reproductive success in anAntirrhinumhybrid zone

Abstract

The maintenance of genetic integrity of parental populations is often explained by selection against hybrids. However, the selection agents are usually unknown. The role of environmental biotic interactions is often suspected but has rarely been demonstrated. In plants for instance, mutualism with pollinators may be involved. After verification that pollen deposition is a limiting factor for fruit set, we used an individual-based study and a representation of pollinator colour perception to test the effects of local plant density and floral colour neighbourhood on female reproductive success in an Antirrhinum hybrid zone. In addition to flower colour and density effects, the composition of the floral neighbourhood was found to influence fruit set, suggesting that most plants were usually better fertilized when similar to their neighbours. However, the plants of one particular type were sometimes favoured when very different from their neighbours. The implications for hybrid zone dynamics are discussed.

The evolutionary history of Antirrhinum in the Pyrenees inferred from phylogeographic analyses

“…majus and A. majus subsp. striatum ), as well as the ecological process that occurs in narrow contact zones [25-27] . Thus, it seems reasonable to assume that the present-day distribution of Antirrhinum in the Pyrenees is the result of historical processes that have taken place across the mountain range and adjacent mountains during Quaternary times.…”

Dynamics and persistence in a metacommunity centred on the plantAntirrhinum majus: theoretical predictions and an empirical test

“…a,b) in our study was comparable to that previously measured in a plant population of A. majus composed of hybrids of the subspecies striatum and pseudomajus by Tastard et al . (), which was ascribed to pollinator limitation. Pollinator limitation may be associated with stochastic changes in pollinator communities, with habitat disturbance, or with other human causes (Ashman et al .…”

“…; Tastard et al . ). Therefore, insect pollination is obligatory in this system, and fruiting is often pollinator‐limited.…”

“…Reproductive isolation in A. majus may be caused by the choice of pollinators (Andalo et al 2010;Suchet et al 2011;Tastard et al 2012Tastard et al , 2014Jaworski et al 2015). In Antirrhinum, the corolla is made of two lobes that close the flower, and only large bees can access the nectar (mostly Bombus spp and Xylocopa violacea, Suchet et al 2011;Tastard et al 2012). Therefore, insect pollination is obligatory in this system, and fruiting is often pollinator-limited.…”

“…We chose to study this network because it provides an excellent opportunity to investigate spatial variation in a tritrophic system. Firstly, A. majus is pollinated by insects (mostly bumblebees), and the rate of pollinator visits limits seed production (Tastard et al 2012). Secondly, this plant produces fruiting capsules on the terminal portion of a rigid stem that persists long after fruiting and keeps the scars of the flowers that did not convert into a fruit, which serves as a measure of the overall plant-pollination success.…”