Do phytogeographic patterns reveal biomes or biotic regions?

Abstract

We present the largest comparative biogeographical analysis that has complete coverage of Australia's geography (20 phytogeographical subregions), using the most complete published molecular phylogenies to date of large Australian plant clades (Acacia, Banksia and the eucalypts). Two distinct sets of areas within the Australian flora were recovered, using distributional data from the Australasian Virtual Herbarium (AVH) and the Atlas of Living Australia (ALA): younger Temperate, Eremaean and Monsoonal biomes, and older southwest + west, southeast and northern historical biogeographical regions. The analyses showed that by partitioning the data into two sets, using either a Majority or a Frequency method to select taxon distributions, two equally valid results were found. The dataset that used a Frequency method discovered general area cladograms that resolved patterns of the Australian biomes, whereas if widespread taxa (Majority method, with >50% of occurrences outside a single subregion) were removed the analysis then recovered historical biogeographical regions. The study highlights the need for caution when processing taxon distributions prior to analysis as, in the case of the history of Australian phytogeography, the validity of both biomes and historical areas have been called into question.

Navigating through chemical space and evolutionary time across the Australian continent in plant genusEremophila

“…phylogenetic clade H) are, with few exceptions including Bontia, Myoporum and a small number of Eremophila species, distributed in arid/semi-arid regions of Australia ( Figure S3). The complex evolutionary history and spatially heterogenous nature of Australia's arid zone is now being recognised [46,47], although dividing the arid biome into smaller areas for biogeographic analysis remains problematic [48]. In the present study, clear geographic patterns emerge between phylogenetic clades A-H ( Figure S3).…”

Carving up Australia's arid zone: a review of the bioregionalisation of the Eremaean and Eyrean biogeographic regions

“…9). These areas were used in a large-scale comparative biogeographic analysis of Eucalyptus, Banksia and Acacia by Murphy et al (2019), who discovered that the relationships of all 21 subregions (excluding New Guinea) support both biomes and historical phytogeographic areas, depending on how widespread taxa are treated in the analyses; once widespread taxa were removed from the analysis, historical phytogeographic areas were recovered. In contrast, clustering of the 21 subregions into clades that closely resembled Australian biomes as defined by Crisp et al (2004), were found if the widespread taxa were left in the analysis.…”

“…In contrast, clustering of the 21 subregions into clades that closely resembled Australian biomes as defined by Crisp et al (2004), were found if the widespread taxa were left in the analysis. The conclusions of Murphy et al (2019) were that widespread taxa have affected the way we view the Australian flora in an evolutionary sense, and may represent more recent distributions that are controlled by climate. The impact of Murphy et al (2019) is not that widespread taxa are driving biomes, but that quantitative data is far more complicated than previously thought, meaning that the data themselves need to be examined and perhaps partitioned before any quantitative analysis is undertaken.…”

“…The conclusions of Murphy et al (2019) were that widespread taxa have affected the way we view the Australian flora in an evolutionary sense, and may represent more recent distributions that are controlled by climate. The impact of Murphy et al (2019) is not that widespread taxa are driving biomes, but that quantitative data is far more complicated than previously thought, meaning that the data themselves need to be examined and perhaps partitioned before any quantitative analysis is undertaken. In addition, this may explain the discrepancy between the criteria of Moore (1961) and the confirmation of Spencer's areas by Kikkawa and Pearse (1969).…”

“…Biogeographers need to allow that the Australian flora contains two or more distinct patterns, which are perhaps temporally discordant. The areas where this pertains to the most are the Eremaean and Eyrean areas for two reasons: (1) the Eremaean and Eyrean are distinctively arid (sensu Burbidge 1960;Crisp et al 2004) and; (2) there are few phylogenetic relationships that support the Eremaean as a natural biotic region (Ebach and Parenti 2015;Murphy et al 2019). In this sense, the Eremaean and Eyrean are biomes, and not historical biogeographic areas, and should therefore not be used as a single large unit or area in historical biogeographic analyses.…”