Las hepáticas y antocerotas (Marchantiophyta y Anthocerotophyta) en la Comunidad Autónoma del País Vasco

Abstract

This study is based on the compilation and revision of the literature, as well as on the many collections that have been made, about 5.500 specimens in all. The Autonomous Community of the Basque Country, occupying 7.482 km2, is a mountainous region (up to 1551 m above sea level) which shows a wide variety of vegetation and climate, ranging from typically oceanic to the mediterranean, with some continental influence in the innermost areas. The lithology is predominantly basic (limestone), but still acid rocks are important, covering 25% of the territory.

Historically, although the first scarce data go back to 1867, the most important contribution was made by the French botanists Allorge, Pierre and Valia, between 1926 and 1935. The catalogue includes 156 taxa, being Lophoziaceae y Lejeunaceae the best represented families. Among these taxa, 15 liverworts and one hornwort are new to the Basque catalogue. The presence in Spain of two species (Cephaloziella elegans and C. rubella) has been confirmed. A number of taxa (23) have been approached for the whole extension of the Iberian Peninsula, most of them are strictly restricted to Northern Spain, and contribute with 29 novelties to 13 different Spanish provinces.

A remarkable character of the liverwort flora in the Autonomous Community of the Basque Country is the high percentage of species with a reduced number of localities. 59% of the taxa are known from less than 10 localities and among them, 15% show just one record. This is a reflection of the rarity of many liverwort species, extremely exigent about their environment and sensitive to its degradation. 25% of the liverwort flora in the studied area is included in any of the threat categories according to Sérgio et al. (1994). In respect to altitude, just 11% lives exclusively above 600 m and even less (5%), above 1000 m; on the other hand, 16% does not ascend beyond 600 m and only four species (2.5%) are restricted to altitudes below 200 m. The usual high humidity requirement by liverworts is granted by the fact that 30% of the taxa lives in areas which receive over 1000 mm annual rainfall and an additional 23% needs more than 1400 mm per year; a meagre 3.5% prefers the driest areas. It is remarkable the presence of a group of termophilous species (15%), which demand a mean temperature in January over 7ºC and another 25% that needs at least a mean temperature in August over 19ºC. Phytogeographically, most species (96.8%) live in the Eurosiberian Region, and 70% does it in exclusive, while only 27% is present in the Mediterranean Region, with just five exclusive species (3.2%). Terricolous species are dominant (35%), as well as the acidophilous (59%). 54% of the taxa are nemoreal, living under different types of woods. Beechwood (Fagus sylvatica) is the favourite for 26% of the total species number. Open plant formations, such as bushy and rocky areas, give shelter to 31% of the taxa.

The analysis of the observed reproductive biology and phenology reveals that a great proportion of taxa (58%) develops complete and mature sporophytes in the studied area. An additional 13% has been found fertile, bearing male and/or female gametangia, and finally 26% of the total catalogue shows any means of specialised organs for vegetative reproduction.

The chorological analysis is based on the elements defined by Hill & Preston (1998). A first gross spectrum shows the distribution of elements by the number of taxa in the catalogue, and a second one ponders the abundance of these taxa in terms of number of localities. The chorological elements enclosed in the temperate zonobiome are dominant (65%/80%), and according to their Eastern distributional limits, circumpolar (33%/31%) and European (23%/29%) taxa are most abundant. The geographical distribution of the chorological elements in the studied area allows to distinguish sectors in the territory. Boreal-montane elements preferentially extend on the mountainous areas. Oceanic and hyperoceanic elements are concentrated in the Northern part, the most humid, sporadically showing some representation on the Northern slopes of the meridional mountains. The widest distribution is that of the temperate and mediterranean/ submediterranean elements.

The analysis of the hotspots in liverwort diversity in the Autonomous Community of the Basque Country shows how the areas with the highest numbers of taxa are, on the one hand, the Northeastern and Eastern areas in Guipúzcoa (Jaizkibel, Peñas de Aia, Leizaran), and, on the other hand, the mountains in the Northern half of the territory, humid and including acid substrates (Gorbea, Ordunte, Urkiola, Aitzkorri, Izarraitz, Hernio-Pagoeta).