Effects of connectivity on animal‐dispersed forest plant communities in agriculture‐dominated landscapes

Abstract

QuestionsHow does connectivity affect animal-dispersed plant assemblages in woodlots of agriculturedominated landscapes? Is this effect dependent on zoochorous dispersal modes? Location Long Term Socio-Ecological Research (LTSER) site of "Zone Atelier Armorique" (ca. 150 km 2 ), Brittany (Western France) Accepted Article MethodsWe sampled 26 small post-agricultural woodlots embedded in an agricultural matrix (1-7 ha).We assessed the connectivity of each woodlot using habitat reachability metrics (i.e., Proportion of Total Potential Dispersal Flux in the Landscape) calculated along a range of dispersal distances from 100 to 1500 m. This metric was based on graph theory, and was calculated as a function of landscape matrix permeability to animal movement (i.e., seed plant dispersal vectors). We analysed the composition of plant assemblages in the core and margins of woodlots. We calculated the proportion of species richness and cover of zoochorous species within these assemblages and for specific zoochorous modes (i.e., epi-, endo-and dyszoochorous species). We analysed the effects of Proportion of Total Potential Dispersal flux at different dispersal distances and woodlot size on the functional dispersal structure of the plant community using linear models. ResultsWe demonstrated that overall plant zoochorous assemblages only depend on woodlot size in the range of dispersal distances tested. The proportion of richness of zoochorous species within the community increased with habitat size. Connectivity influenced only the relative proportions of the different zoochorous modes, except for the dyszoochorous group, which was primarily influenced by woodlot size. Both epizoochorous and endozoochorous species were impacted by the interaction between connectivity and woodlot area. Connectivity increased the proportion of epizoochorous species richness and the proportion of endozoochorous cover in assemblages in big woodlots. These effects were detected at short dispersal distances. Our results were supported in both total and core plant assemblages. ConclusionThis study indicates that both habitat isolation and decrease in habitat size contribute towards shaping the functional structure of the plant community, but they act at different levels of dispersal mode. Our results suggest that in these fragmented landscapes long-distance dispersal has been lost either because of the selection of small-sized animal movements or of the rareness of plant species needing large habitat size. Maintaining woodlot connectivity in the woodland surroundings seems to be sufficient to preserve short-distance dispersal though a more thorough restoration of landscape connectivity is necessary to recover the functional composition of the community with the whole set of dispersal patterns.

Coupling landscape graph modeling and biological data: a review

“…Once the connectivity metrics have been computed, biological data are considered as target variables in a statistical analysis in which connectivity metrics are used as explanatory variables. Examples of such a hypothetico-deductive approach can be seen in Martín-Queller and Saura (2013) or Mony et al (2018). Separating the connectivity modeling step and the use of biological data amounts to considering connectivity, measured by metrics, as a potential driver of the biological response.…”

“…Estrada-Peña 2005;Betbeder et al 2017) in habitat patches by including connectivity metrics in a regression model. In some cases concerning birds or plants, regression or correlation analyses performed at the community level attest to the effect of connectivity either on patch richness (Mony et al 2018) or on an inter-patch dissimilarity measure (Muratet et al 2013). Of the papers referring to the deductive approach, only a smallish proportion (27%) includes a sensitivity analysis to evaluate how statistical dependence is influenced by cost values (Foltête and Giraudoux 2012), minimum patch size (Anderson and Bodin 2009), the distance of graph pruning (Koh et al 2013;Muratet et al 2013) or the setting of the dispersal kernel in the metric calculation (Martín-Queller et al 2017;Gil-Tena et al 2014).…”

Additive effects of connectivity provided by different habitat types drive plant assembly

“…We sampled plant assemblages in woodlands in 2013 (some of these data are already published in Mony et al . 24 ) and in temporary grasslands and wheat croplands in 2016.…”

“…8,9,23 and Mony et al . 24 ). These functional indices still consider that species which co-exist in plant communities may occupy different ecological niches and rely on different habitats to disperse 25 .…”

Estudios de conectividad del paisaje en América Latina: retos de investigación

“…Comprender y analizar los estudios orientados a la conectividad del paisaje permitiría crear programas y acciones orientados a la conservación de los ecosistemas a un menor costo, dado que la conectividad permite preservar las especies durante periodos prolongados y coadyuvaría al flujo e intercambio de especies entre hábitats dentro de un paisaje fragmentado. La conectividad es esencial y fundamental para el desarrollo de poblaciones viables de cualquier especie que requieran espacios de dispersión amplios o grupos de especies de tamaño más grandes (Hatfield et al, 2018;Mony et al, 2018). Por ello, es importante realizar un trabajo que revise el estado del arte, las tendencias y características de investigación sobre conectividad del paisaje para orientar esfuerzos en la conservación de los ecosistemas.…”