Abstract
AbstractAimsLandscape fragmentation has strong negative consequences on biodiversity. In networks of linear elements, connectivity loss results in a decreased length of connected elements and increased potential barriers, directly impacting the ability of plants to disperse. However, species vary in their tolerance to connectivity loss, likely due to differences in dispersal strategies. We investigated whether species tolerance to decreased ditch network connectivity is determined by seed traits. We selected, as a case study, water‐dispersed plant species in a ditch network.LocationDitch network in an intensive agricultural area in northern France.MethodsWe selected 27 sites of 500 m × 500 m, where we calculated connectivity indices based on the length of connected ditches, intersections and culvert number. For each parameter, we calculated plant tolerance levels by analysing species changes in occurrence in response to change in connectivity values. Concurrently, we measured in laboratory conditions five seed traits involved in plant movement and establishment in standing aquatic systems and analysed their explanatory power in plant tolerance to fragmentation.ResultsAll traits were significantly related to at least one component of ditch network connectivity. We interpreted the following two strategies in plant tolerance to connectivity loss from the results: (1) in networks where the connected network length was short, plants displayed short‐distance dispersal with less efficient sexual reproduction, probably in favour of local vegetative multiplication; and (2) in networks with a high density of culverts or intersections, plants displayed seeds with reduced local retention, where seeds had the capacity to overcome long and frequent trapping events. In highly branched networks, plants also exhibited higher germination rates, promoting seed establishment when trapped along the banks. Seed capacity to be dispersed by wind at the water surface was only a marginal factor in plant tolerance to fragmentation.ConclusionsConnectivity loss acted as a filter on species seed traits. The results of our study offer an enhanced understanding of plant dispersal in fragmented standing aquatic networks and emphasize the importance of developing functional approaches in landscape studies.
Highlights
Landscape fragmentation resulting from decreased habitat size and increased isolation of habitat patches is unequivocally recognized as a major driver of biodiversity loss (Debinski & Holt 2000; Fahrig 2003; Fischer & Lindenmayer 2007)
Culvert number within the 100 m catchment area exhibited no influence on plant species occurrence
Projected coefficients varied from round (Brassica nigra; Galium palustre) to long and thin (Glyceria maxima; Sparganium erectum) seeds
Summary
Landscape fragmentation resulting from decreased habitat size and increased isolation of habitat patches is unequivocally recognized as a major driver of biodiversity loss (Debinski & Holt 2000; Fahrig 2003; Fischer & Lindenmayer 2007). Reduced connectivity decreases the ability of propagules originating from the regional species pool to reach a specific location (Damschen et al 2008). These factors might result in strong negative demographic (Brown & KodricBrown 1977; Dornier & Cheptou 2012) and deleterious genetic (Richards 2000; Newman & Tallmon 2001) consequences on populations, impacting plant species persistence and occurrence at the metapopulation level (Jacquemyn et al 2003; Piessens et al 2005; Lindborg et al 2014). More work is needed in characterising dispersal mechanisms to better elucidate how dispersal traits mediate species’ response to connectivity loss
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