Impacts of Mating Behavior on Plant–Animal Seed Dispersal Mutualisms

Ottewell²,

Sork

et al. 2018

Molecular Ecology

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Seed and pollen dispersal shape patterns of gene flow and genetic diversity in plants. Pollen is generally thought to travel longer distances than seeds, but seeds determine the ultimate location of gametes. Resolving how interactions between these two dispersal processes shape microevolutionary processes is a long-standing research priority. We unambiguously isolated the separate and combined contributions of these two dispersal processes in seedlings of the animal-dispersed palm Oenocarpus bataua to address two questions. First, what is the spatial extent of pollen versus seed movement in a system characterized by long-distance seed dispersal? Second, how does seed dispersal mediate seedling genetic diversity? Despite evidence of frequent long-distance seed dispersal, we found that pollen moves much further than seeds. Nonetheless, seed dispersal ultimately mediates genetic diversity and fine-scale spatial genetic structure. Compared to undispersed seedlings, seedlings dispersed by vertebrates were characterized by higher female gametic and diploid seedling diversity and weaker fine-scale spatial genetic structure for female gametes, male gametes and diploid seedlings. Interestingly, the diversity of maternal seed sources at seed deposition sites (N ) was associated with higher effective number of pollen sources (N ), higher effective number of parents (N ) and weaker spatial genetic structure, whereas seed dispersal distance had little impact on these or other parameters we measured. These findings highlight the importance maternal seed source diversity (N ) at frugivore seed deposition sites in driving emergent patterns of fine-scale genetic diversity and structure.

Section: Discussionsupporting

confidence: 56%

Section: Methodsmentioning

confidence: 99%

The relative contributions of seed and pollen dispersal to gene flow and genetic diversity in seedlings of a tropical palm

Ottewell²,

Sork

et al. 2018

Molecular Ecology

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“…), with occasional primary dispersal by kinkajous ( Potos flavus ), small rodents and oilbirds ( Steatornis caripensis , J. Karubian and L. Browne, unpublished data). Umbrellabirds, which are rare outside of pristine habitat (BirdLife International ; Walter et al., ), are capable of long‐distance seed dispersal, with maximum estimated dispersal distances of >1 km in continuous forest in our study area (Karubian & Durães, ; Karubian et al., ). Umbrellabirds generate genetically heterogeneous seed pools at traditional display sites known as leks Karubian, Sork, Roorda, Durães, & Smith, ; Scofield, Smouse, Karubian, & Sork, ).…”

Section: Methodsmentioning

confidence: 86%

Habitat loss and fragmentation reduce effective gene flow by disrupting seed dispersal in a neotropical palm

Karubian

2018

Molecular Ecology

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Habitat loss and fragmentation often reduce gene flow and genetic diversity in plants by disrupting the movement of pollen and seed. However, direct comparisons of the contributions of pollen vs. seed dispersal to genetic variation in fragmented landscapes are lacking. To address this knowledge gap, we partitioned the genetic diversity contributed by male gametes from pollen sources and female gametes from seed sources within established seedlings of the palm Oenocarpus bataua in forest fragments and continuous forest in northwest Ecuador. This approach allowed us to quantify the separate contributions of each of these two dispersal processes to genetic variation. Compared to continuous forest, fragments had stronger spatial genetic structure, especially among female gametes, and reduced effective population sizes. We found that within and among fragments, allelic diversity was lower and genetic structure higher for female gametes than for male gametes. Moreover, female gametic allelic diversity in fragments decreased with decreasing surrounding forest cover, while male gametic allelic diversity did not. These results indicate that limited seed dispersal within and among fragments restricts genetic diversity and strengthens genetic structure in this system. Although pollen movement may also be impacted by habitat loss and fragmentation, it nonetheless serves to promote gene flow and diversity within and among fragments. Pollen and seed dispersal play distinctive roles in determining patterns of genetic variation in fragmented landscapes, and maintaining the integrity of both dispersal processes will be critical to managing and conserving genetic variation in the face of continuing habitat loss and fragmentation in tropical landscapes.

“…Although we did not assess movement, it is probable that many of the birds we detected utilized a wider network of habitat beyond the fragment where observed (Chaves‐Campos , Karubian et al . , Karubian & Durães ). All birds we studied are forest‐dependent species (BirdLife International ), and tree cover outside of fragments accounted for the increase of one additional frugivore species per 13 percent additional surrounding tree cover.…”

Section: Discussionmentioning

confidence: 94%

Landscape‐level tree cover predicts species richness of large‐bodied frugivorous birds in forest fragments

Walter

Freile³

et al. 2017

Biotropica

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Large‐bodied frugivorous birds play an important role in dispersing large‐sized seeds in Neotropical rain forests, thereby maintaining tree species richness and diversity. Conversion of contiguous forest land to forest fragments is thought to be driving population declines in large‐bodied frugivores, but the mechanistic drivers of this decline remain poorly understood. To assess the importance of fragment‐level versus local landscape attributes in influencing the species richness of large‐bodied (>100 g) frugivorous birds, we surveyed 15 focal species in 22 forest fragments (2.7 to 33.6 ha, avg. = 16.0 ha) in northwest Ecuador in 2014. Fragment habitat variables included density of large trees, canopy openness and height, and fragment size; landscape variables included elevation and the proportion of tree cover within a 1 km radius of each fragment. At both the individual species level, and across the community of 12 species of avian frugivore we detected, there was higher richness and probability of presence in fragments with more tree cover on surrounding land. This tendency was particularly pronounced among some endangered species. These findings corroborate the idea that partially forested land surrounding fragments may effectively increase the suitable habitat for forest‐dwelling frugivorous birds in fragmented landscapes. These results can help guide conservation priorities within fragmented landscapes, with particular reference to retaining trees and reforesting to attain high levels of tree cover in areas between forest patches.