Pohlia section Cacodon (Mielichhoferiaceae, Bryophyta) with axillary bulbils in the Iberian Peninsula

Guerra, J. 2007. Pohlia section Cacodon (Mielichhoferiaceae, Bryophyta) with axillary bulbils in the Iberian Peninsula. Anales Jard. Bot. Madrid 64(1): 55-62. A taxonomic and descriptive study is presented of the propaguliferous species –with axillary bulbils– of section Cacodon of the genus Pohlia in the Iberian Peninsula. Among the nine species of this section present in the Iberian Peninsula, seven produce axillary propagula (bulbils). The propagulum morphology, seen to be the most relevant gametophyte identification character, is described. Data are provided on the habitat and distribution of the species in the Iberian Peninsula, where they are considered

In this article we provide morphological, chorological and ecological data that broaden the knowledge of these propaguliferous species in a territory where they are infrequent and probably undercollected.

Material and Methods
All the available material (65 specimens) of the studied species deposited in the Iberian herbaria have been studied.In addition, all the lectotypes of the species that it was possible to locate were studied.The bulbils were photographed with a SPOT INSIGHT U3.5 digital camera mounted on an OLYMPUS BH2 microscope.Measurement of the leaves, cells, etc., were made with a micrometer attached to the same microscope.

Pohlia
Habitat.Generally on sandy, acid and very wet soils on stream banks and, in very clear running water in high mountains of the northern Iberian Peninsula, sometimes on humid banks permanently covered with melting snow.A very rare species in the Iberian Peninsula; only known from the Pyrenees and north Portugal.
Habitat.Acid soils, sometimes calcareous, on talus and in bare patches in pastures and meadows, generally shaded, humid sites in high and medium mountains.Relatively frequent in the Iberian Peninsula.
Observations.Obconic bulbils, with leaf primordia arising only in the apex is a characteristic of Pohlia andalusica and therefore useful for identification purposes.
Habitat.Acid soils, on taluses and on bare ground in pastures and meadows, shaded, wet sites generally near streams and springs.Relatively frequent in the Iberian Peninsula.

Pohlia flexuosa
Habitat.Acid soils on very humid, shaded taluses.Observations.Only known from two localities in the Iberian Peninsula, one near Girona (Casas, 1996) and that studied here.
Pohlia flexuosa produces up to three diferent types of bulbil, usually mixed (at least in material studied) in the axils of upper and middle leaves.These types have been interpreted as different stages of propagule development (Wilczek & Demaret, 1970;Townsend, 1995).However, in Smith (2004) and Hill & al. (2006) these propagule types are given taxonomic value to differentiate two varieties of Pohlia flexuosa: var.flexuosa and var.pseudomuyldermansii (Arts, Nordhorn-Richter & A.J.E.Sm.) A.J.E.Sm.
The vermicular propagules of P. flexuosa look like those of P. proligera, although the latter are broader [(10-15(20) μm in P. flexuosa and 30-35 μm in P. proligera] and the apical cells are much longer.
Habitat.Acid soils, sometimes calcareous on humid and shaded taluses.
Habitat.Acid soils, sometimes calcareous on wet and shaded taluses, frequently covered with herbaceous vegetation.Pohlia proligera is a much more northern species, and in the Iberian Peninsula only appear at higher elevations compared to P. annotina.
Observations.The bulbils of this species are characteristic, although they may resemble those Pohlia annotina in the early stages of development.It is therefore necessary to observe a considerable number of bulbils to avoid confusion.Another character to dis-tinguish P. proligera from P. annotina is the very shiny leaves of P. proligera, which permits a distinction even when bulbils are lacking.

Conclusions
To date, a group of seven species of Pohlia from the section Cacodon can be characterized in the Iberian Peninsula according to differences in size, number, morphology, etc. of their axillary bulbils.Species of this group are very similar to one another in such features as habit, size, leaf sheen, shape, leaf cell size and shape.In most cases species are not easily recognizable in the absence of bulbils.Table 1 summarises the most relevant differentiating characteristics of all the species studied.