Life history variation across a riverine landscape: intermediate levels of disturbance favor sexual reproduction in the ant‐dispersed herbRanunculus ficaria

Abstract

Global climate change can fundamentally alter disturbance regimes across landscapes, but little is known about how species adjust their life histories to shifts in disturbance regimes. In plants, dispersal by seeds may permit rapid re-colonization under frequent disturbances, but often seed-dispersing animals may be absent and local dispersal by vegetative diaspores may be a more efficient means of occupying open space in the vicinity of the plant. We tested the effect of disturbances due to inundation on the investment in seed production by the ant-dispersed plant, Ranunculus ficaria ssp. bulbifer. During seed ripening we collected 392 plants within a landscape mosaic of 39 sites with different levels of inundation. We measured the mass of fruits and other tissues (leafs, roots, bulbils, stalks) and described plant growth form. We found that fruit numbers and masses were more variable among plants than numbers and masses of other tissues. We then standardized fruit mass against the mass of other tissues and other growth-form parameters. Standardized fruit mass showed a highly significantly hump-shaped relationship with the level of inundation disturbances. This pattern was consistent across 12 small-scale transects and thus not confounded by spatial autocorrelation within landscapes. The pattern was also confirmed by analyses that simultaneously accounted for disturbance and morphological co-variables. We thus conclude that plants invested most heavily into reproduction by seeds under intermediate levels of disturbance. Under intermediate disturbance, seeds are beneficial for rapidly recolonizing open space after disturbance while the seed-dispersers are still available. The life history of mutualists such as ant-dispersed plants and ants may thus change across a landscape, reflecting small-scale variation in the disturbance regime.

Natural hybridization between diploid Ficaria calthifolia and tetraploid Ficaria verna subsp. verna in central Europe

“…Indeed, the pattern in the production of well-developed achenes in parental and hybrid plants cultivated in a common garden closely matched that of pollen viability. Our estimates of number and percentage of well-developed achenes per collective fruit agree almost perfectly with other reports on F. calthifolia (Drenckhahn 2016) but differ from several reports on F. *verna (Marsden-Jones 1935, Taylor & Markham 1978, Wcisło & Pogan 1981, Jung et al 2008, but see Drenckhahn 2016. This is particularly curious when an average of 23% of well-developed achenes per collective fruit were recorded by us in F. *verna compared to the 7% and 2% that are reported by Wcisło & Pogan (1981) and Marsden-Jones (1935), respectively.…”

“…Although several factors (e.g. genetic differences between populations, different environmental and weather conditions and disturbance; Jung et al 2008) might explain the discrepancies in seed-set estimations between studies, we guess that both ours and Drenckhahn (2016) estimates of achene production in F. *verna are characteristic of the situation in genetically diverse populations with intensive intra-and perhaps also interspecific outcrossing (Popelka et al 2019).…”

How do steppe plants follow their optimal environmental conditions or persist under suboptimal conditions? The differing strategies of annuals and perennials

“…In annuals, small seeds favored both capacities. Small seeds might indeed provide a dual function: due to their undirected dispersal, they may frequently end up in any environmental conditions, including suboptimal ones, and due to their wide unassisted dispersal, small seeds may help to colonize distant patches of optimal environmental conditions, notably in the absence of reliable animal vectors (Jung, Böhning‐Gaese, & Prinzing, ). However, all these traits come at a cost.…”

Soil characteristics drive Ficaria verna abundance and reproductive output

“…Ficaria verna may be a particularly successful invasive due to its multiple reproductive strategies; besides forming seeds, it also produces tubers and aboveground bulbils. Under intermediate disturbance, F. verna invests more heavily in the production of seeds (Jung et al 2008). When resources are not readily available for sexual reproduction, asexual bulbils are produced in place of seeds, and in some cases, the amount of bulbils produced is inversely related to the amount of seeds produced (Arizaga and…”