Diversity, Distribution, Systematics and Conservation Status of Podocarpaceae

Abstract

Among conifer families, Podocarpaceae is the second largest, with amazing diversity and functional traits, and it is the dominant Southern Hemisphere conifer family. However, comprehensive studies on diversity, distribution, systematic and ecophysiological aspects of the Podocarpaceae are sparse. We aim to outline and evaluate the current and past diversity, distribution, systematics, ecophysiological adaptations, endemism, and conservation status of podocarps. We analyzed data on the diversity and distribution of living and extinct macrofossil taxa and combined it with genetic data to reconstruct an updated phylogeny and understand historical biogeography. Podocarpaceae today contains 20 genera and approximately 219 taxa (201 species, 2 subspecies, 14 varieties and 2 hybrids) placed in three clades, plus a paraphyletic group/grade of four distinct genera. Macrofossil records show the presence of more than 100 podocarp taxa globally, dominantly from the Eocene-Miocene. Australasia (New Caledonia, Tasmania, New Zealand, and Malesia) is the hotspot of living podocarps diversity. Podocarps also show remarkable adaptations from broad to scale leaves, fleshy seed cones, animal dispersal, shrubs to large trees, from lowland to alpine regions and rheophyte to a parasite (including the only parasitic gymnosperm-Parasitaxus) and a complex pattern of seed and leaf functional trait evolution.

Keywords: IUCN red list; climate change; conifers; conservation; fossils; historical biogeography; paleo-endemism; phylogenetics; physiology.

Figure 1

The phylogenetic relationships and divergence time of the 20 extant podocarp genera within Podocarpaceae. Blue node bars indicate the 95% highest posterior density divergence time estimates for the corresponding node. Branch lengths are proportional to time (Ma, millions of years).

Figure 2

Diagram of two-way cluster analysis. The vertical matrix axis consists of more than 200 podocarp species coded by scientific name and the horizontal axis is the distributed countries (74 countries). The matrix was constructed depending on the presence (black) and absence (white). The species were grouped into five main clusters, I. New Caledonian group, II. New Zealand group and III. Malesian group, IV. Southeast Asian group and V. Podocarpian group.

Figure 3

(A) Dacrycarpus dacrydioides (White pine, Kahikatea) tree in the rainforest of Wellington Kaitoke Regional Park, New Zealand. (B) Microcachrys tetragona (Strawberry pine) is a creeping shrub in the alpine region of cradle mountain summit, Tasmania.

Figure 4

(A) Podocarpus lawrencei in the alpine region, Mount McKay Falls Creek, Australia. (B) Pherosphaera hookeriana and Microcachrys tetragona populations in the alpine region of Cradle Mountain summit, Tasmania.

Figure 5

The proportion of current IUCN conservation status of Podocarpaceae species. The conservation status is evaluated according to IUCN Red List categories and criteria, version 3.1 (IUCN Council, Geneva, Switzerland).

Figure 6

A wildfire in 2020 burnt the Tahune rainforest, Tasmania. This photo is of a burnt Celery-top Pine (Phyllocladus aspleniifolius) tree.