Significance of gametophyte form in long-distance colonization by tropical, epiphytic ferns

Dassler. C. L. & D. R. Farrar (Department of Botany, Iowa State University, Ames. Iowa 50011 U.S.A.). Significance of gametophyte form in long-distanc e colonization by tropical, epiphytic ferns. Brittonia 53: 352-369. 2001.-G ametophyte morphology of tropical epiphytic ferns may confer an advantage f or establishment on islands, Most tropical, epiphytic ferns belong to five families: Hymenophyllaceae, Grammitidaceae, Vittariaceae, Polypodiaceae, an d Elaphoglossaceae. Gametophytes of these families are long-lived and clone -forming. In addition, most Hymenophyllaceae, Grammitidaceae, and Vittariac eae produce dispersible gemmae. Each of these characteristics increases opp ortunity for outbreeding, and when island floras are statistically compared with floras of adjacent mainlands. island floras are found to be rich in e piphytic species possessing gemmae (Hymenophyllaceae, Grammitidaceae, and V ittariaceae), and depauperate in epiphytic species lacking gemmae (Polypodi aceae and Elaphoglossaceae). We propose that gametophytic gemmae significan tly aid long-distance colonization of outbreeding species because gemmae 1) allow gametophytes to exploit available niches through dispersal of gemmae , and through clonal expansion and persistence of the resulting gametophyte , and 2) facilitate sexual reproduction by providing the opportunity for sp erm and antheridiogen transfer when gametophytes are distant, and by provid ing a new source of tissue for antheridia formation.