Gerardo Rivas

Geographical patterns and determinants of species richness in Mexico across selected families of vascular plants: implications for conservation

Mexico is considered a megadiverse country containing more than 10% of the worlds biodiversity. The distribution of this species richness and endemism is different among the different Mexican states. We examined the species richness patterns of 13 families of vascular plants (including ferns, gymnosperms and angiosperms) in Mexico using political divisions (states) as units of analysis. We analysed the species richness values (absolute richness, endemic richness and restrictive richness) of these plant families using stepwise multiple regression analysis, assessing their relationship with a set of 10 environmental variables (expressed as heterogeneity coefficients). A combined cluster analysis with multidimensional scaling analysis (MDS) and an analysis of similarities were also undertaken to define the spatial–geographical patterns. Additionally, we proposed a methodological strategy to determine which states of Mexico have priorities for conservation. Our results suggested that the three species richness values used were significantly predicted by environmental factors, especially by climatic heterogeneity. Notwithstanding that a linear pattern was recognized, the Mexican states were gathered in four groups, which were confirmed by the MDS and the cluster analysis: (1) the Yucatan Peninsula, (2) arid Mexico, (3) the Mexican Transition Zone and (4) the megadiverse states. We proposed that 12 Mexican states include all the environmental conditions and are candidates for developing conservation programmes: (1) Quintana Roo, Tabasco and Yucatán, (2) Baja California, Chihuahua and Sinaloa, (3) Guerrero, Jalisco and Nuevo León and (4) Chiapas, Oaxaca and Veracruz.

The Dermacentor (Acari, Ixodida, Ixodidae) of Mexico: hosts, geographical distribution and new records

Abstract Distribution and host data from published literature and previously unpublished collection records are provided for all nine species of the Holarctic tick genus Dermacentor that are known to occur in Mexico, as well as two species that may occur there. Parasite-host and host-parasite lists are presented, together with a gazetteer of collection localities and their geographical coordinates.

Diversity, endemism and conservation of ferns (Polypodiales) in the Mexican Mountain Component

We analyzed the distributional patterns of 95 selected species of leptosporangiate ferns inhabiting the Mexican Mountain Component, using grid-cells of one geographical degree as unit areas, applying endemism indices and richness and beta diversity analyses. Distributional data were obtained from several herbaria and specialized literature. Five grid-cells appear to be important for fern species richness, as they contain 35 to 49 species. These grid-cells are located in the Sierra Madre Oriental (SMO), Trans-Mexican Volcanic Belt (TMVB) and the Sierra Madre del Sur (SMS). Mean richness by latitudinal belts of one degree showed that the belts with highest values are related to the TMVB and SMS. A total of 13 grid-cells were recognized as important from the perspective of endemism; most of them are located also in the SMO, TMVB and SMS. The richest gridcells coincided with one of the main centres of endemism for ferns obtained in this study, located in the convergence of the southern part of the SMO, the eastern portion of the TMVB and the northern part of the SMS, reflecting the high humidity existing on the mountain slopes facing the Gulf of Mexico. Some important grid-cells recognized from richness and endemism analyses coincide with Mexican Natural Protected Areas. The beta diversity analysis showed a low degree of similarity among grid-cells, implying a high species replacement, as the result of environmental heterogeneity occurring in the Mexican mountain systems. On the other hand, the spatial analysis suggested a pattern of phytogeographical regionalization comprising two main areas: the Mexican Transition Zone and the Mexican Central Plateau. Ferns play an important role in the Mexican biodiversity and contributing to the beta diversity of Mexico.

Myobiid mites (Trombidiformes, Myobiidae) of the golden bat Mimon cozumelae from Mexico. Description of the male and tritonymph of Ioanella mimon and new records of Eudusbabekia mimon

Abstract The male and the tritonymph of Ioanella mimon are described for the first time parasitizing to Mimon cozumelae from Yucatan, Mexico. Male of Ioanella mimon is characterized by the presence of legs I with the tibia and tarsus fused forming a small complex devoided of apical claws, legs II–IV with two claws, setae vi at level of anterior end of genital plate, genital plate rounded with an anterior projection, all intercoxal setae short; while the tritonymph is characterized by the presence of legs I unequal; legs II–IV with 2-1-1 claws, and posterior region of dorsal idiosoma with 3 pairs of cylindrical and toothed setae. Additionally, we include new locality and host records for Eudusbabekia mimon which was also found on Mimon cozumelae. Both species were described originally in association with Mimon bennettii at Bartica, Guyana.

Patterns in attachment sites of the parasite Hydrachna guanajuatensis Cook, 1980 (Acari: Hydrachnidiae) on aquatic heteropterans (Nepomorpha) from the Tecocomulco Lake, Mexico

The water mite Hydrachna guanajuatensis Cook, 1980 is recorded as an ectoparasite of Ranatra sp. (Nepidae), Notonecta sp., Buenoa sp. (Notonectidae), Krizousacorixa femorata (Guérin, 1857), Trichocorixella mexicana (Hungerford, 1927), and Hesperocorixa laevigata (Uhler, 1893) (Corixidae). The host body region, where the larvae and protonymph attach, depends significantly on the heteropteran species: χ2 = 3969.43, p < 0.05 and χ2 = 1893.6, p < 0.05, respectively. We performed a cross tabulation with a correspondence analysis and found three associations for the larvae: 1) dorsal side of abdomen underneath the wings of the two species of Notonectidae, 2) head, wings, and hind legs of two of the species of Corixidae (T. mexicana and K. femorata), and 3) thorax and fore and middle legs of the single species of Nepidae. These different patterns are discussed according to morphological and ecological characteristics of the hosts. This is the first study that deals with the spatial distribution patterns within the same species of ectoparasite.