Reproductive resilience to habitat fragmentation of Lithraea molleoides (Anacardiaceae), a dominant dioecious tree from the Chaco Serrano

Abstract

Most of the earth´s surface has been transformed by man into urbanized and cultivated areas, decreasing and fragmenting the remaining natural habitats. These changes result in decreased plant population sizes and increased isolation among remaining populations. Because dioecious plant species have male and female flowers in different individuals, they are obligately outcrossing and highly dependent on pollination vectors. Thus, reductions in population size and changes in their sex ratio after deforestation can be significantly drastic for their reproduction. While much research has been conducted assessing habitat fragmentation effects on sexual reproduction of populations of hermaphrodite species, very little is known about the effects on dioecious species. Here, we simultaneously assessed habitat fragmentation effects on the phenological patterns, sex ratios, reproductive ecology and progeny performance of the Chaco Serrano dominant native dioecious tree Lithraea molleoides. In contrast to our initial hypotheses, we found that neither conspecific flowering density, sex ratios, nor flowering phenology of L. molleoides was affected by habitat fragmentation. Lastly, progeny performance was not affected by habitat fragmentation either. Our overall findings across three reproductive seasons show that this dioecious species is resilient to changes imposed by habitat fragmentation. We discuss the particular combination of ecological traits of L. molleoides that may be conferring reproductive resilience, such as ambophilous pollination system and the capability of asexual seed production through apomixis, which may be shared by other woody native dioecious species.