Conservation genetics and ecology of an endemic montane palm on Lord Howe Island and its potential for resilience

Abstract

Lepidorrhachis mooreana (Arecaceae) is a monotypic palm genus endemic to the remote Lord Howe Island where it is restricted to a small area of cloud forest above 750 m that is likely to be vulnerable to climate change. We investigated genetic diversity and key demographic parameters to assess the palm's potential long term viability including possible climate change impacts. The palm was found on only one of the island's two mountain summits, where the sampled sites were effectively behaving as one panmictic population. The moderate genetic diversity found indicates some adaptive potential for L. mooreana. The population was effectively inbred. Large numbers of fruit are produced, but successful juvenile recruitment is limited by predation by introduced rats. The relatively large population size increases the potential for selection for adaptation to a changing climate.

Will Climate Change, Genetic and Demographic Variation or Rat Predation Pose the Greatest Risk for Persistence of an Altitudinally Distributed Island Endemic?

“…The other LHI palms have similarly low levels of genetic differentiation [6,72]. Hedyscepe canterburyana is abundant on LHI with good connectivity throughout its distribution.…”

“…The number of infructescences produced per individual in a year for H. canterburyana was comparable to that of close relative Rhopalostylis sapida [ 29 ]. Hedyscepe canterburyana has a comparable, though slightly greater proportion of individuals with reproductive structures present than the other Lord Howe Island palms [ 6 , 72 ]. Reproduction was variable between years with 24% of the H. canterburyana individuals ( RI ) having reproductive structures in 2008, compared with 44% in 2010.…”

“…The genetic diversity in H. canterburyana is comparable, though moderately higher, than has been reported for endemic palms from the Seychelles, Vanuatu and Canary Islands [ 41 , 75 ]. Hedyscepe canterburyana has similar levels of genetic diversity compared with the other Lord Howe Island endemic palms [ 5 , 6 , 72 ] and also widespread Mexican palms that are considered to have higher levels of variation compared to other tropical plants [ 76 , 77 ].…”

“…Low genetic differentiation reported here is similar to palms sampled across small spatial distances in Mexico and Brunei [ 76 , 78 ]. The other LHI palms have similarly low levels of genetic differentiation [ 6 , 72 ]. Hedyscepe canterburyana is abundant on LHI with good connectivity throughout its distribution.…”

“…Inbred yet genetically diverse populations of Belize palm Chamaedorea ernesti-augusti were explained by thrip pollinators movement among different groups of inflorescences in different years [ 81 ]. Inbreeding may also be due to a mixed mating system, pollination between close relatives or self-pollination between male and female flowers on the same plant [ 72 , 82 ]. Self-compatibility may enable a selection advantage whereby the frequency of genotypes that are successful under strong climate change selection can be increased [ 83 ].…”