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Knowledge about the herbaceous layer in relation to environmental factors in West African savannas is still scarce. Early life-cycle events like germination of the herbaceous species are of special interest, as these stages can play critical roles in establishing of the plants and determine population and community dynamics. We aim to assess intraspecific differences in the germinability of herbaceous savanna species with respect to environmental conditions to reveal adaptations in this early life cycle stage. The study was conducted in the Sudanian savanna of Burkina Faso in West Africa. We collected seeds of two annual herbs (Chamaecrista mimosoides, Spermacoce stachydea) along a climatic gradient from different habitats and land use types and conducted germination experiments under equal conditions in climate chambers. For both species several environmental factors showed a significant impact on the germination rates. While higher precipitation caused an increase in the germination rate only for S. stachydea, habitat conditions had a significant influence for both species. Intermediate habitats with balanced soil moisture caused an enhancement of the germination success. Moreover shrub cover had a positive effect on the germinability of C. mimosoides, whereas the germinability of S. stachydea decreased due to an increasing herbaceous cover. The study showed that certain environmental factors are able to modify the intraspecific variability of the germinability trait, which might affect the establishment of the species populations.
Agrobiont spider species are well adapted to arable systems, which have fairly uniform vegetation structure and pest assemblages over continent-wide areas. We wanted to study, whether agrobiont spider subassemblages and the life history of the most prominent agrobiont, Pardosa agrestis, show any regional variation within Hungary, where only modest climatic differences exist between the NW and SE parts of the country. We studied agrobiont species of spider assemblages in 27 alfalfa and 21 cereal fields with suction sampling and pitfalls. The similarity structure of these agrobiont sub-assemblages (Sørensen distance measure) was congruent with the geographic distance matrices (Eucledian distance), as tested by Mantel tests. However, if we considered sub-assemblages consisting of the non-agrobiont species, this congruency was always higher. Thus, agrobionts responded only moderately to geographical variation if we compare them to non-agrobiont species. We studied the generation numbers and the occurrence of the first adult individuals in P. agrestis; the most common agrobiont spider in Hungary. This comparison involved comparing fields along a NW – SE gradient during 6 sampling years in pairwise comparisons, where in each year a northern and a southern population was compared with a minimum distance of 126 km in between. In generation numbers there was no difference; we found two generations across Hungary. In contrast, the first occurrence of adult individuals was on average 15 days earlier in both generations in the more southern populations. Thus, it can be concluded that agrobionts show a fairly stable and relatively low magnitude response over country-sized geographical ranges.