Two-scale modelling of Saponaria bellidifolia Sm. (Caryophyllaceae) abundance on limestone outcrops from its northern range periphery (Southeastern Carpathians)

Abstract

We modelled the effect of habitat heterogeneity on the abundance of the submediterranean Saponaria bellidifolia, a red list species in Romania. The study was designed at two scales: 100 and 0.5 m 2 . At larger scale, generalized additive models and canonical correspondence analysis were used to model the density of ramets, whereas at microscale, binomial logistic regression was employed to model the species' occurrence. S. bellidifolia abundance responded sensitively to habitat type (classified as ''grassy'', ''rocky'' and ''scree''), rather than to microclimatic variables. At both scales, habitat type was the best predictor of ramet abundance, followed by slope and vegetation cover. At 0.5 m 2 , soil depth was also a good predictor of species occurrence. The data revealed that screes are the most suitable habitats for hosting relatively large populations of this rare species, because of occasional natural disturbances and presumably lower interspecific competition.

Positive relationship between genetic- and species diversity on limestone outcrops in the Carpathian Mountains

“…One source of this weak relationship might consist in differences in resource availability and disturbance among outcrops that seem to have contrasting effects on individual populations. In the intermediate-sized POS site, shallow soils and frequent fires may have lowered to a great extent species diversity as also reported by Schwilk et al (1997) and Lundholm and Larson (2003) in similar systems; in contrast, the genetic diversity of S. bellidifolia may have benefited from disturbances due to increased population patchiness (Csergő et al, 2009a).…”

“…Likewise, expected heterozigosity (H exp ) followed a similar pattern with values ranging between 0.101 in SC-BEL and 0.022 in URD (see Csergő et al, 2009a for more details).…”

“…It is a rare habitat specialist whose local abundance is strongly affected by habitat heterogeneity and disturbance (Csergő et al, 2009a).…”

“…Our results support this view. The genetic diversity was enhanced by the number of plant communities and was probably driven by substantial differences in abundance of S. bellidifolia individuals under contrasting habitat conditions (Csergő et al, 2009a). Indeed, habitat patchiness may have significant effects on genetic diversity and may be a source of important evolutionary events in habitat specialists such as S. bellidifolia (Lö nn et al, 1996).…”