[The fate of subspecies category in zoological systematics. 2. The present].

The present approach to the use of subspecies category in zoological systematics is an integrative one. It counts as obligatory to confirm the validity of subspecies, defined by morphological data, with genetic criteria. This allows marking out those subspecies that really exist as separate monophyletic population groups. As a result, the system would be cleared of many 'phantom' taxa established in course of non-critical use of the subspecies concept. However, detailed analyses of intra-species variability by methods of molecular taxonomy in many cases reveal a quite complicated divergence pattern which cannot be adequately described in terms of the classic scheme of 'species and its subspecies'. Keeping in mind the irregularity of intra-species divergence rate when dealing with molecular and morphological traits, it is proposed to use an extended system of subspecies taxa when describing 'extra complicated' situations. In addition to a 'subspecies' such categories as 'allospecies', 'morphotype', 'morphospecies' may be used for which operational definitions are suggested. As an example, the micro-systematics of the great pond snails (the complex Lymnaea stagnalis s. lato) from Palaearctic region is examined. The provisional system of this group, developed by the author, is based on morphological and phylogeographical data. Applying the series of subspecies categories of different level allows reflecting with maximal completeness the intra-species variability of great pond snails and, to some extent, the process of their genetic divergence and geographic range forming. The second part of the article deals with modern approaches to subspecies category usage in zoological systematics as well as the problems of so called micro-systematics, i.e., systematics operating at the lowest level of categories such as ones of subspecies and infra-subspecies rank (Mayr, 1982).

Prediction of prevalence from mean abundance via a simple epidemiological model in mesostigmate mites from two geographical regions.

We analysed data on the abundance and distribution of 26 species of mesostigmate mites with different feeding habits collected from bodies of small mammalian hosts in 2 geographical regions (West Siberia and Argentina). We tested whether prevalence of a mite can be reliably predicted from a simple epidemiological model that takes into account mean abundance and its variance. We theorized that the difference between prevalence predicted from the model and observed prevalence would be smallest in obligatory haematophagous mites, intermediate in facultatively haematophagous mites and greatest in non-haematophagous mites. We also theorized that prevalence of mites from the region with sharp seasonality (Siberia) would be predicted accurately only if host number would be taken into account. We found that the success of a simple epidemiological model to predict prevalence in mites was similar to that reported earlier for other ectoparasitic arthropods. Surprisingly, the model predicted prevalence of obligatory exclusively haematophagous mites less successfully than that of mites with other feeding habits. No difference in the model performance between mites occurring in the 2 geographical regions were found independent of whether the model took the number of hosts into account.

Searching for general patterns in parasite ecology: host identity versus environmental influence on gamasid mite assemblages in small mammals.

The abundance and diversity of parasites vary among different populations of host species. In some host-parasite associations, much of the variation seems to depend on the identity of the host species, whereas in other cases it is better explained by local environmental conditions. The few parasite taxa investigated to date make it difficult to discern any general pattern governing large-scale variation in abundance or diversity. Here, we test whether the abundance and diversity of gamasid mites parasitic on small mammals across different regions of the Palaearctic are determined mainly by host identity or by parameters of the abiotic environment. Using data from 42 host species from 26 distinct regions, we found that mite abundances on different populations of the same host species were more similar to each other than expected by chance, and varied significantly among host species, with half of the variance among samples explained by differences between host species. A similar but less pronounced pattern was observed for mite diversity, measured both as species richness and as the taxonomic distinctness of mite species within an assemblage. Strong environmental effects were also observed, with local temperature and precipitation correlating with mite abundance and species richness, respectively, across populations of the same host species, for many of the host species examined. These results are compared to those obtained for other groups of parasites, notably fleas, and discussed in light of attempts to find general rules governing the geographical variation in the abundance and diversity of parasite assemblages.