Climate predictions accelerate decline for threatened macrozamia cycads from queensland, australia.

Melinda Laidlaw,Paul Forster

doi:10.3390/biology1030880

Abstract

Changes in the potential habitat of five allopatric species of threatened Macrozamia cycads under scenarios of increased ambient temperature were examined. A lack of seed dispersal, poor recruitment, low seedling survival, obligate pollinator mutualisms and continued habitat loss have led to extant populations being largely restricted to refugia. Models predict that the area of suitable habitat will further contract and move upslope, resulting in a reduced incidence within protected areas with increasing annual mean temperature. Areas of potential habitat for all five species are also predicted to become increasingly isolated from one another, further reducing the exchange between metapopulations and subpopulations, exacerbating existing threatening processes.

Highlights

The cycads (Cycadophyta: families Cycadaceae, Zamiaceae [1]) comprise dioecious, long-lived woody gymnosperms that have a perennial caudex or trunk and leaves that are shed and renewed over a period of several years. &\FDGV FDQ EH FRQVLGHUHG DV μIODJVKLS VSHFLHV¶ IRU FRQVHUYDWLRQ biology [2,3], as they have unusual life histories, are generally restricted in distribution, with over 50%of species threatened globally [4,5], and are of commercial interest to horticulture
It is perhaps unlikely that disjunct populations of most cycad species behave as part of a dynamic μPHWDSRSXODWLRQ¶, where the local populations are regularly connected by dispersing individuals or have a flow of genetic material with the potential to recolonise or augment adjacent populations [17±19]
All species models performed significantly better than random when compared to 1000 null models of randomly selected locations from masks used for background point selection (Table 1)

Summary

Introduction

The cycads (Cycadophyta: families Cycadaceae, Zamiaceae [1]) comprise dioecious, long-lived woody gymnosperms that have a perennial caudex or trunk and leaves that are shed and renewed over a period of several years. &\FDGV FDQ EH FRQVLGHUHG DV μIODJVKLS VSHFLHV¶ IRU FRQVHUYDWLRQ biology [2,3], as they have unusual life histories, are generally restricted in distribution, with over 50%. These five species occur allopatrically in generally consistent habitat types, but appear to share common reproductive traits of thermogenic male and female cones and a common pollinating beetle (the weevil Tranes) [31±33] and are probably biologically compatible if individuals from populations could interact genetically. They may be the result of a relatively recent speciation event [29], probably post-Pleistocene, as has been proposed for other cycads [11,27,34]. SRSXODWLRQV DQG PD\ LQ UHDOLW\ EH WKH μOLYLQJ GHDG¶ LQ D ELRORJLFDO VHQVH SDUWLFXODUO\ LI WKH REOLJDWH pollinators have been lost from individual populations

Experimental Section

Results and Discussion

Conclusions