Petra Dieker

Poleward range expansion without a southern contraction in the ground beetle Agonum viridicupreum (Coleoptera, Carabidae).

Abstract We investigated the extent of poleward shifts in the distribution range of Agonum viridicupreum due to climate change in the western Palaearctic. Species’ records were obtained from extensive literature sources as well as from collections, and consistent amateur entomologists’ recordings. Within the general geographic range of the species, we analyzed in detail two parts of both, the northern and southern distribution range boundaries: (1 and 2) north-western Germany (leading or high-latitude edge), (3) Israel and (4) southern Italy (rear or low-latitude edge). Temporal changes in the occurrence data of the species indicated a northward shift of the leading edge of a minimum of 100 km within the last 50 to 100 years. In contrast, according to the data gathered, the rear edge has not changed during the last decades. Further studies are needed in order to fully understand the underlying mechanisms of the different behaviour of leading and rear range edges of Agonum viridicupreum in the current context of global change. Despite our incomplete understanding, chronosequences of the occurrence of the given species have the potential to optimize climate niche modelling to predict trends in the distribution range in the future.

Spatial analyses of two color polymorphisms in an alpine grasshopper reveal a role of small-scale heterogeneity

Abstract Discrete color polymorphisms represent a fascinating aspect of intraspecific diversity. Color morph ratios often vary clinally, but in some cases, there are no marked clines and mixes of different morphs occur at appreciable frequencies in most populations. This poses the questions of how polymorphisms are maintained. We here study the spatial and temporal distribution of a very conspicuous color polymorphism in the club‐legged grasshopper Gomphocerus sibiricus. The species occurs in a green and a nongreen (predominately brown) morph, a green–brown polymorphism that is common among Orthopteran insects. We sampled color morph ratios at 42 sites across the alpine range of the species and related color morph ratios to local habitat parameters and climatic conditions. Green morphs occurred in both sexes, and their morph ratios were highly correlated among sites, suggesting shared control of the polymorphism in females and males. We found that in at least 40 of 42 sites green and brown morphs co‐occurred with proportions of green ranging from 0% to 70% with significant spatial heterogeneity. The proportion of green individuals tended to increase with decreasing summer and winter precipitations. Nongreen individuals can be further distinguished into brown and pied individuals, and again, this polymorphism is shared with other grasshopper species. We found pied individuals at all sites with proportions ranging from 3% to 75%, with slight, but significant variation between years. Pied morphs show a clinal increase in frequency from east to west and decreased with altitude and lower temperatures and were more common on grazed sites. The results suggest that both small‐scale and large‐scale spatial heterogeneity affects color morph ratios. The almost universal co‐occurrence of all three color morphs argues against strong effects of genetic drift. Instead, the data suggest that small‐scale migration–selection balance and/or local balancing selection maintain populations polymorphic.

A review of ecological gradient research in the Tropics: identifying research gaps, future directions, and conservation priorities

The Tropics are global centers of biodiversity. Ecological and land use gradients play a major role in the origin and maintenance of this diversity, yet a comprehensive synthesis of the corresponding large body of literature is still missing. We searched all ISI-listed journals for tropical gradient studies. From the resulting 1023 studies, we extracted study-specific information, and analyzed it using descriptive analytical tools and GLMs. Our results reveal that dry tropical areas are vastly understudied compared to their humid counterparts. The same holds true for large parts of Africa, but also the Philippines and the South Asian region. However, we also found that (applied) research output of developing tropical countries is nowadays on par with the output of developed countries. Vegetation and elevation were the most studied response variable and gradient, respectively. By contrast, inconspicous organisms such as oribatid mites and edaphic gradients were largely missing in the literature. Regarding biodiversity, tropical gradient studies dealt extensively with species richness and ecosystem diversity, but much less with genetic diversity. We encourage a wider use of modern statistical learning tools such as non-linear (spatio-temporal) regression and classification techniques, and simulations. Finally, we would embrace an even further development of synergies between applied and basic research and between researchers based in developed and in tropical countries.