Anthropogenic habitat disturbance is a strong biodiversity change driver that compromises not only the species persistence but also the ecological interactions in which they are involved. Even though seed dispersal is a key interaction involved in the recruitment of many tree species and in consequence critical for biodiversity maintenance, studies assessing the effect of different anthropogenic disturbance drivers on this interaction have not been performed under a meta-analytical framework. We assessed the way habitat fragmentation and degradation processes affect species diversity (abundance and species richness) and interaction rates (i.e., fruit removal and visitation rates) of different groups of seed-disperser species at a global scale. We obtained 163 case studies from 37 articles. Results indicate that habitat degradation had a negative effect on seed-disperser animal diversity, whereas habitat fragmentation had a negative effect on interaction rates. Birds and insects were more sensitive in terms of their diversity, whereas mammals showed a negative effect on interaction rates. Regarding habitat, both fragmentation and degradation had a negative effect on seed-disperser animal diversity only in temperate habitats, and negative effects on interaction rates in tropical and temperate habitats. Our results indicate that the impact of human disturbance on seed-disperser species and interactions is not homogeneous. On the contrary, the magnitude of effects seems to be dependent on the type of disturbance, taxonomic group under assessment, and geographical region where the human impact occurs.
Abstract. Anthropogenic disturbance can modify habitat structure and resource availability, potentially disrupting ecological interactions. This issue may be critical for pollination and seed dispersal, which determine natural regeneration. The mistletoe Tristerix corymbosus is almost exclusively pollinated by a hummingbird (Sephanoides sephaniodes) and dispersed by a marsupial (Dromiciops gliroides). We examined the extent to which human-induced habitat change and resource availability influence the interaction rate of this plant-pollinator-seed disperser system, along a forest transformation gradient (from native forest to exotic plantations). We estimated visitation rates of S. sephaniodes and D. gliroides on 70 T. corymbosus mistletoes using camera traps. We related visitation rates to habitat structural features and resource availability (flowers and fruits of the mistletoe and the neighborhood) using spatially explicit models. Sephanoides sephaniodes and D. gliroides visitation rates responded positively to shrub and bamboo cover, moss abundance, and mistletoe spatial arrangement. Pollination and seed dispersal interactions were sensitive to the flower and fleshy-fruit neighborhoods, being variable across months. Further, D. gliroides showed a non-random spatial association with fleshy-fruited plants. A larger sunlight incidence on disturbed habitats may prevent the disruption of key ecological interactions by increasing resource availability. This effect would result from the presence of shade-intolerant plants, which are benefited by sunlight exposure. Patches of disturbed habitat may enhance landscape heterogeneity, providing complementary resources to the native remnants.
2019. The hidden costs of living in a transformed habitat: ecological and evolutionary consequences in a tripartite mutualistic system with a keystone mistletoe. Science of the Total Environment 651 (P2) , pp.
Habitat structure determines species occurrence and behavior. However, human activities are altering natural habitat structure, potentially hampering native species due to the loss of nesting cavities, shelter or movement pathways. The South American temperate rainforest is experiencing an accelerated loss and degradation, compromising the persistence of many native species, and particularly of the monito del monte (Dromiciops gliroides Thomas, 1894), an arboreal marsupial that plays a key role as seed disperser. Aiming to compare 2 contrasting habitats (a native forest and a transformed habitat composed of abandoned Eucalyptus plantations and native understory vegetation), we assessed D. gliroides' occurrence using camera traps and measured several structural features (e.g. shrub and bamboo cover, deadwood presence, moss abundance) at 100 camera locations. Complementarily, we used radio telemetry to assess its spatial ecology, aiming to depict a more complete scenario. Moss abundance was the only significant variable explaining D. gliroides occurrence between habitats, and no structural variable explained its occurrence at the transformed habitat. There were no differences in home range, core area or inter-individual overlapping. In the transformed habitats, tracked individuals used native and Eucalyptus-associated vegetation types according to their abundance. Diurnal locations (and, hence, nesting sites) were located exclusively in native vegetation. The landscape heterogeneity resulting from the vicinity of native and Eucalyptus-associated vegetation likely explains D. gliroides occurrence better than the habitat structure itself, as it may be use Eucalyptus-associated vegetation for feeding purposes but depend on native vegetation for nesting.
G. L. Stebbins' most effective pollinator principle states that when pollinators are not limiting, plants are expected to specialize and adapt to the most abundant and effective pollinator species available. In this study, we quantify the effectiveness of bees, hummingbirds and hawkmoths in a Chilean population of (Phrymaceae), and examine whether flower traits are subject to pollinator-mediated selection by the most effective pollinator species during two consecutive years. Unlike most species in the pollinator community, the visitation rate of the recently arrived did not change substantially between years, which together with its high and stable pollen delivery to flower stigmas made this species the most important in the pollinator assemblage, followed by the solitary bee Flower traits were under significant selection in the direction expected for short-tongue bees, suggesting that is in the initial steps of adaptation to the highly effective exotic bumblebee Our results illustrate the applicability of Stebbins' principle for new invasive pollinators, and stress their importance in driving flower adaptation of native plant species, a critical issue in the face of biotic exchange and homogenization.
Habitat fragmentation and degradation are important biodiversity change drivers worldwide. Their effects have been described for many animal groups, but little is known about marsupials. We conducted a meta-analysis aiming to evaluate the actual effects of habitat fragmentation and degradation on forest marsupials. From a literature survey, we obtained 85 case studies reporting disturbance comparisons. We found a negative overall effect, as well as a negative effect for habitat fragmentation, but not for habitat degradation. Marsupials from Oceania were negatively affected by habitat disturbance, whereas there was no effect for those from South America. Arboreal marsupials were negatively affected, whereas terrestrial marsupials did not. Species from the families Dasyuridae (Antechinus spp.) and Microbiotheriidae (Dromiciops gliroides) showed to be sensitive to habitat disturbance.
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