Schizaeaceae: a phylogenetic approach

Abstract

Schizaeaceae fossils have been documented throughout Mesozoic and Cenozoic deposits, but our understanding of this fossil record is hampered by uncertainties with respect to the relationships of living species. To start building a phylogenetic framework for the family, an initial phylogenetic analysis of living species using plastid rbcL nucleotide sequence data is conducted. The analysis supports Schizaea s. lat. and Lygodium monophyly, but Anemia is resolved as paraphyletic to Mohria. In the Anemia/ Mohria clade, monophyly of subgenus Anemiorrhiza is supported, but Coptophyllum is resolved as paraphyletic to subgenus Anemia. In Schizaea s. lat., both Schizaea s. str. and Actinostachys are well supported and Microschizaea is grouped with Schizaea s. str., although only one Microschizaea species ( Schizaea pusilla) was included. These results are largely congruent with previous morphology-based analyses. In Lygodium however, results presented contrast with recent morphological analyses highlighting the problems of identifying Lygodium subgeneric groups. Using the resulting phylogeny as a framework, putative relationships of fossil species are discussed, tentative minimum age estimates for generic crown group diversifications are made, and possible conclusions with respect to the origins of habit and habitat preferences are discussed. The fossil evidence indicates that subgeneric groups within the Anemia/ Mohria clade are comparatively ancient, originating during the Early Cretaceous, and the putative placement of fossil Anemia within the crown group of living subgenus Anemiorrhiza would indicate that their calcareous habitat preference may be a relic feature that has persisted ever since the Early Cretaceous. Lygodium on the other hand appears to have passed through a diversity bottleneck. Modern species diversity probably originated in the Neogene, and the earliest fossil evidence for the origin of their vining and trailing habit comes from the placement of Miocene fossil Lygodium within the crown group of living species.