Seventy species distributed among 7 genera currently compose the family Splachnaceae. Although many species are restricted to dung or other animal remains for a substrate, others are terricolous or epiphytic. Coprophilous species exhibit a series of "adaptations" to their unique habitat: they produce chemicals that attract insects that look for dung to lay their eggs; the sterile tissue below the sporangium is expanded allowing for insects to land on the sporophyte; they produce small sticky spores; their capsule wall contracts upon drying and the spores are continupously pushed up to the mouth of the sporangium by a psuedocolumellea subtending the spore mass. Entomochorous taxa (i.e., those that use insects to disperse their spores) have traditionally been considered derived within the family, with Splachnum representing the ultimate product of this evolutionary trend. Here we present phylogenetic analyses of sequences of two chloroplast loci (trnL-trnF and rps4) for about 100 accessions, including exemplars of all genera considered closely related to the Splachnaceae. Maximum parsimony and likelihood analyses yield topologies wherein Splachnum is resolved sister to a clade comprising all remaining taxa. Within the latter, Tetraplodon whose species are all thought to be entomophilous too, is sister to the Taylorioideae. Brachymitrion, the sole genus lacking any feature associated with entomophily, and occurring primarily in epiphytic habitst, composes the most derived lineage. Most noticeable is the recurrent association of anemophilous (using wind for spore dispersal) and entomophilous species. Based on these results it is hypothesized that entomophily was acquired early in the evolutionary history of the Splachnaceae and subsequently lost multiple times. This scenario would suggest that although highly specialized taxa may be evolutionary dead ends, that they offer a source for subsequent evolution of less specialized taxa, and thus may play in a significant part in the diversification of these lineages.

Key words: Bryophytes, dung-mosses, entomochory, evolution, phylogeny, Splachnaceae