Toni Safner

Comparison of Bayesian clustering and edge detection methods for inferring boundaries in landscape genetics

Recently, techniques available for identifying clusters of individuals or boundaries between clusters using genetic data from natural populations have expanded rapidly. Consequently, there is a need to evaluate these different techniques. We used spatially-explicit simulation models to compare three spatial Bayesian clustering programs and two edge detection methods. Spatially-structured populations were simulated where a continuous population was subdivided by barriers. We evaluated the ability of each method to correctly identify boundary locations while varying: (i) time after divergence, (ii) strength of isolation by distance, (iii) level of genetic diversity, and (iv) amount of gene flow across barriers. To further evaluate the methods’ effectiveness to detect genetic clusters in natural populations, we used previously published data on North American pumas and a European shrub. Our results show that with simulated and empirical data, the Bayesian spatial clustering algorithms outperformed direct edge detection methods. All methods incorrectly detected boundaries in the presence of strong patterns of isolation by distance. Based on this finding, we support the application of Bayesian spatial clustering algorithms for boundary detection in empirical datasets, with necessary tests for the influence of isolation by distance.

Combining demography and genetic analysis to assess the population structure of an amphibian in a human-dominated landscape

In this article, we applied demographic and genetic approaches to assess how landscape features influence dispersal patterns and genetic structure of the common frog Rana temporaria in a landscape where anthropogenic perturbations are pervasive (urbanization and roads). We used a combination of GIS methods that integrate radiotracking and landscape configuration data, and simulation techniques in order to estimate the potential dispersal area around breeding patches. Additionally, genetic data provided indirect measures of dispersal and allowed to characterise the spatial genetic structure of ponds and the patterns of gene flow across the landscape. Although demographic simulations predicted six distinct groups of habitat patches within which movement can occur, genetic analyses suggested a different configuration. More precisely, BAPS5 spatial clustering method with ponds as the analysis unit detected five spatial clusters. Individual-based analyses were not able to detect significant genetic structure. We argue that (1) taking into account that each individual breeds in specific breeding patch allowed for better explanation of population functioning, (2) the discrepancy between direct (radiotracking) and indirect (genetic) estimates of subpopulations (breeding patches) is due to a recent landscape fragmentation (e.g. traffic increase). We discuss the future of this population in the face of increasing landscape fragmentation, focusing on the need for combining demographic and genetic approaches when evaluating the conservation status of population subjected to rapid landscape changes.

Are the dinaric mountains a boundary between continental and mediterranean wild boar populations in Croatia

Wild boar is the most important large game species in Croatia, with populations subjected to hunting/management programs. There are indications from previous analyses of morphological variation and reproductive performance that population structure of wild boar in Croatia is strongly influenced by the Dinaric mountain range that separates Croatia in two biogeographic regions: Continental and Mediterranean. Of the two main wild boar haplogroups found in Europe, the most widespread is the E1 clade (present from Portugal to Russia), while the E2 clade is found within the Italian peninsula and on Sardinia. Outside Italy, the E2 clade has to date been found only in archaeological samples from the Mediterranean region of Croatia. The aims of this study were to investigate the hypotheses that (i) the Dinaric Mountains act as a natural boundary separating the Continental and Mediterranean wild boar subpopulations in Croatia; and (ii) the mtDNA E2 clade is present in Croatian wild boar. A total of 14 unlinked microsatellite loci were examined in 264 geo-referenced individuals, and the 486-bp fragment of the mtDNA control region sequence was examined in 69 individuals. The results suggest that the region of the Dinaric Mountains. represents a weak boundary between the Continental and Mediterranean subpopulations, and that the predominant factor causing the observed genetic structuring is isolation by distance. Based on these results, it can be proposed that the Croatian wild boar population in the mainland should be managed as a whole. Three variable sites and four haplotypes were obtained from the mtDNA sequences, all of which belonged to the major European clade (E1).

Locomotor activity pattern of two recently introduced non-native ungulate species in a Mediterranean habitat

Abstract. The aim of this study was to determine the locomotor activity pattern of European mouflon and axis deer in a Mediterranean habitat on the island of Rab, and to determine the temporal overlap between these two species. Nine cameras with an infrared motion detection system were used to track animal activity over a 12-month period, 24 hours per day. A total of 122082 JPEG photographs were obtained, of which 69273 recorded the presence of the two target non-native ungulate species. The average monthly number of recorded animals varied by sex and season for European mouflon and by season for axis deer. Both species displayed a bimodal activity pattern, with an overlap coefficient of 0.74 for the activity of both species during the entire study period. The results indicate a non-competitive coexistence and similar activity patterns in the studied ungulate species, despite the high overlap coefficient.

Efficiency of alpha designs in Croatian variety trials

Regulations of variety trials in Croatia prescribe RCBD as the only possible trial design. This could cause many problems, especially when a large number of varieties have to be tested. In order to explore the possibilities of improving the efficiency of variety trials through the use of alternative trial design, RCBD was substituted by alpha design in a project funded by the Ministry of Agriculture and Forestry.