2. Molecular Genetics and the Conservation of Diversity
25
identify geographic areas within which populations of species comprising ecological communities have had evolutionary histories separate from those elsewhere in
the range. Where such a history of vicariance occurs, independently evolving communities can be recognised. Further, priorities for management can be set according to the degree of congruence among species, the magnitude of divergence, or
some combination of these (Moritz and Faith 1998). This approach to recognising
the historical component of genetic diversity can, in principle, be combined with
assessments based on diversity of species and communities to identify a set of areas
that are representative of all three tiers of diversity. Within these areas, management should then ensure that functional, ecologically and environmentally heterogeneous landscapes are retained in order to protect viability and promote continued
adaptive evolution. In the fotlowing, I illustrate the basis and application of this
approach using data from rainforest faunas of the sUbtropical and tropical coast of
Australia.
4 Evolution and Conservation of Rainforest
Faunas
4.1 The Vertebrates of the Wet Tropics of Australia
The tropical rainforests of north-east Australia are small in extent « 1M ha), yet
harbour a high diversity of species, many of which are endemic (Commonwealth of
Australia 1986; Nix and Switzer 1991). Besides the high endemicity, other attributes that make this a useful system with which to explore evolutionary processes and strategies for conserving genetic diversity are; (i) a strong background of
paleo-ecology, providing evidence for fluctuations in the distribution and composition of rainforests during the climatic fluctuations of the Quaternary (Kershaw 1994;
Hopkins et al. 1993), (ii) a reasonably stable alpha taxonomy and good information
on species distributions (e.g .. Webb and Tracey 1981; Nix 1991; Williams et al.
1996), and (iii) accumulating data from mtDNA on patterns of phylogeography
within endemic species of vertebrates (Moritz et al. 1993; Joseph and Moritz 1994;
Joseph et al. 1995; Schneider et al. 1998; Schneider and Moritz 1999).
The analyses of phylogeography in several species of bird, frog and lizard have
revealed strong and geographically congruent separation of populations to the north
and south of a historical disjunction of rainforests predicted by paleoclimatological
modelling ("Black Mountain Corridor", BMC, Fig. 2). Levels of sequence divergence at mtDNA protein coding genes vary from <1% to 2% in birds to between
3% and 12% in frogs and lizards. For most of the herpetofauna examined, this
implies several million years of separation, whereas more recent (Pleistocene) separations are inferred for the birds. In general, the magnitude of separation is inversely proportional to presumed vagility and positively related to the degree of
specialisation to rainforests. In addition to the general vicariance pattern about the
BMC, there are additional more species-specific breaks in phylogeography at other
25
identify geographic areas within which populations of species comprising ecological communities have had evolutionary histories separate from those elsewhere in
the range. Where such a history of vicariance occurs, independently evolving communities can be recognised. Further, priorities for management can be set according to the degree of congruence among species, the magnitude of divergence, or
some combination of these (Moritz and Faith 1998). This approach to recognising
the historical component of genetic diversity can, in principle, be combined with
assessments based on diversity of species and communities to identify a set of areas
that are representative of all three tiers of diversity. Within these areas, management should then ensure that functional, ecologically and environmentally heterogeneous landscapes are retained in order to protect viability and promote continued
adaptive evolution. In the fotlowing, I illustrate the basis and application of this
approach using data from rainforest faunas of the sUbtropical and tropical coast of
Australia.
4 Evolution and Conservation of Rainforest
Faunas
4.1 The Vertebrates of the Wet Tropics of Australia
The tropical rainforests of north-east Australia are small in extent « 1M ha), yet
harbour a high diversity of species, many of which are endemic (Commonwealth of
Australia 1986; Nix and Switzer 1991). Besides the high endemicity, other attributes that make this a useful system with which to explore evolutionary processes and strategies for conserving genetic diversity are; (i) a strong background of
paleo-ecology, providing evidence for fluctuations in the distribution and composition of rainforests during the climatic fluctuations of the Quaternary (Kershaw 1994;
Hopkins et al. 1993), (ii) a reasonably stable alpha taxonomy and good information
on species distributions (e.g .. Webb and Tracey 1981; Nix 1991; Williams et al.
1996), and (iii) accumulating data from mtDNA on patterns of phylogeography
within endemic species of vertebrates (Moritz et al. 1993; Joseph and Moritz 1994;
Joseph et al. 1995; Schneider et al. 1998; Schneider and Moritz 1999).
The analyses of phylogeography in several species of bird, frog and lizard have
revealed strong and geographically congruent separation of populations to the north
and south of a historical disjunction of rainforests predicted by paleoclimatological
modelling ("Black Mountain Corridor", BMC, Fig. 2). Levels of sequence divergence at mtDNA protein coding genes vary from <1% to 2% in birds to between
3% and 12% in frogs and lizards. For most of the herpetofauna examined, this
implies several million years of separation, whereas more recent (Pleistocene) separations are inferred for the birds. In general, the magnitude of separation is inversely proportional to presumed vagility and positively related to the degree of
specialisation to rainforests. In addition to the general vicariance pattern about the
BMC, there are additional more species-specific breaks in phylogeography at other