Leon R. Perrie

In the Southern Hemisphere there has been little phylogeographical investigation of forest refugia sites during the last glacial. Hooker's spleenwort, Asplenium hookerianum, is a fern that is found throughout New Zealand. It is strongly associated with forest and is a proxy for the survival of woody vegetation during the last glacial maximum. DNA sequence data from the chloroplast trnL-trnF locus were obtained from 242 samples, including c. 10 individuals from each of 21 focal populations. Most populations contained multiple, and in many cases unique, haplotypes, including those neighbouring formerly glaciated areas, while the predominant inference from nested clade analysis was restricted gene flow with isolation by distance. These results suggest that A. hookerianum survived the last glacial maximum in widespread populations of sufficient size to retain the observed phylogeography, and therefore that the sheltering woody vegetation must have been similarly abundant. This is consistent with palynological interpretations for the survival in New Zealand of thermophilous forest species at considerably smaller distances from the ice sheets than recorded for the Northern Hemisphere. Eastern and central North Island populations of A. hookerianum were characterized by a different subset of haplotypes to populations from the remainder of the country. A similar east-west phylogeographical pattern has been detected in a diverse array of taxa, and has previously been attributed to recurrent vulcanism in the central North Island.

Abstract Aim To examine the relative importance of long‐distance dispersal in shaping the New Zealand pteridophyte (ferns and lycophytes) flora and its relationships with other floras, with the null hypothesis that the extant New Zealand pteridophyte flora has been isolated since New Zealand’s separation from Gondwana. Location New Zealand. Methods rbc L DNA sequences were assembled for 31 New Zealand pteridophyte genera, with each genus represented by one New Zealand species and the most closely related non‐New Zealand species for which data were available. Maximum‐likelihood, maximum‐parsimony, and Bayesian analysis phylograms were constructed and used as input for r 8 s molecular dating, along with 23 fossil calibrations. Divergence estimates less than conservatively recent ages for New Zealand’s geological isolation, namely H o > 30 Ma for pairs involving New Caledonian and Norfolk Island species and H o > 55 Ma for all others, were taken as rejection of the null hypothesis. Results The null hypothesis was rejected for all pairs except, under some parameter conditions, for those involving the New Zealand species Cardiomanes reniforme , Lindsaea trichomanoides , Loxsoma cunninghamii , Lygodium articulatum , Marattia salicina , and Pteris comans . However, the Lindsaea and Pteris results probably reflect the absence in the analyses of closely related non‐New Zealand samples, while the Marattia divergence was highly contingent on which fossil calibrations were used. Main conclusions Rejection of the null hypothesis for the majority of pairs implies that the extant New Zealand lineage has undergone long‐distance dispersal either into or out of New Zealand. The notion of a long isolation since geological separation can, therefore, be dismissed for much of New Zealand’s pteridophyte flora. The analyses do not identify the direction of the long‐distance dispersal, and these New Zealand lineages could have had vicariant origins with subsequent long‐distance emigration. However, the alternative that many extant New Zealand pteridophyte lineages only arrived by long‐distance immigration after geological isolation seems likely.

Nucleotide sequences of the chloroplast trnL-trnF intergenic spacer were obtained for 21 of the 22 indigenous Asplenium taxa presently recognized from New Zealand. Nucleotide sequences of the chloroplast rbcL gene were also obtained from eleven New Zealand species representative of the diversity found in the trnL-trnF intergenic spacer. Phylogenetic analyses of these chloroplast sequence data indicate that the Asplenium species of New Zealand are not monophyletic. More specifically, the Asplenium species participating in hybridization in New Zealand form a closely related ‘Austral’ group, whereas the non-hybridizing species have closer affinities to species from outside New Zealand. Within the Austral group, three well-supported sub-groups are recognized, represented by the species A. bulbiferum, A. flaccidum, and A. obtusatum. Dating analyses reject an 80 million year old vicariant origin for any of the Asplenium lineages in New Zealand, and the distributions of the many Asplenium species disjunct between New Zealand and elsewhere appear best explained by long-distance dispersal. The likely chloroplast/maternal parent for each of the New Zealand octoploid species is discussed.