2. Molecular Genetics and the Conservation of Diversity
27
river valley which has probably been unsuitable for cool adapted rainforest vertebrates for much of the past 5,000 years (Nix 1991; Winter 1997).
To consider the adaptive axis of genetic diversity, we can use as a surrogate
patterns of morphological variation. Comparisons of several traits, including
ecomorphological characters and those typically used by taxonomists, in three species of lizard revealed no significant divergence across the BMC other than for a
single scale character in one species (Schneider and Moritz 1999). The same lack
of morphological divergence across the BMC is evident for frogs (M. Cunningham,
unpublished data) and is inferred for birds from the lack of recognised sub-species
distributed to either side of the BMC. This observation casts doubt on the role of
isolation and drift in promoting divergence and is inconsistent with the refuge
model of speciation as originally proposed for rainforest vertebrates (Haffer 1969;
Schneider and Moritz 1999). It also provides a vivid illustration of the need to
consider separately the historical and adaptive axes of diversity. This is emphasised
further by a recent comparison of molecular and morphological variation in another species oflizard endemic to the wet tropics (c. Schneider, T. Smith, B. Larrison
and C. Moritz, unpublished data). In this species, Carlia rubigularis, morphological divergence across the BMC was trivial, despite sequence divergence of 12%. In
contrast, highly significant shifts in body size and shape was observed between
popUlations in adjacent rainforest and open forest despite high levels of gene flow.
This echoes recent observations of increased morphological divergence of birds
across ecotones relative to that within rainforests (Smith et al. 1997) and points to
the need to protect diverse habitats within areas in order to maintain adaptive diversity among populations.
From the above information, it is clear that to protect the historical axis of
genetic diversity in wet tropics ver1ebrates, we should prioritise areas to the north
and south of the BMC. To maintain the process of adaptive divergence, we should
ensure that maximum diversity of vegetation communities are protected within
each area. A more detailed analysis (Moritz and McDonald, in press) using the
quantitative approach described by Moritz and Faith (1998) identified as key areas
for protecting historical diversity the Finnegan Uplands to the north, the Atherton
Uplands to the south and the geographically intermediate Malbon Thompson range
(Fig. 2). By contrast, analyses of patterns of complementarity of endemic species of
vertebrate across the same area identified a different set of priority areas, the northern Thornton and Carbine Uplands and the Bellenden Ker Range, in particular
(Moritz and McDonald, in press; Fig. 2). This illustrates that genetic and species
components of diversity are not equivalent, presumably because of distinct determinants operating on different spatial and temporal scales. Both should be considered in conservation planning. However, once the set of areas that adequately
capture both species and (historical) genetic diversity are identified, the notion that
habitat heterogeneity should be maximised within areas is consistent with both
maintaining adaptive diversity and maximising the diversity of species (Williams
1997; Williams and Pearson 1997) and ecosystems.
27
river valley which has probably been unsuitable for cool adapted rainforest vertebrates for much of the past 5,000 years (Nix 1991; Winter 1997).
To consider the adaptive axis of genetic diversity, we can use as a surrogate
patterns of morphological variation. Comparisons of several traits, including
ecomorphological characters and those typically used by taxonomists, in three species of lizard revealed no significant divergence across the BMC other than for a
single scale character in one species (Schneider and Moritz 1999). The same lack
of morphological divergence across the BMC is evident for frogs (M. Cunningham,
unpublished data) and is inferred for birds from the lack of recognised sub-species
distributed to either side of the BMC. This observation casts doubt on the role of
isolation and drift in promoting divergence and is inconsistent with the refuge
model of speciation as originally proposed for rainforest vertebrates (Haffer 1969;
Schneider and Moritz 1999). It also provides a vivid illustration of the need to
consider separately the historical and adaptive axes of diversity. This is emphasised
further by a recent comparison of molecular and morphological variation in another species oflizard endemic to the wet tropics (c. Schneider, T. Smith, B. Larrison
and C. Moritz, unpublished data). In this species, Carlia rubigularis, morphological divergence across the BMC was trivial, despite sequence divergence of 12%. In
contrast, highly significant shifts in body size and shape was observed between
popUlations in adjacent rainforest and open forest despite high levels of gene flow.
This echoes recent observations of increased morphological divergence of birds
across ecotones relative to that within rainforests (Smith et al. 1997) and points to
the need to protect diverse habitats within areas in order to maintain adaptive diversity among populations.
From the above information, it is clear that to protect the historical axis of
genetic diversity in wet tropics ver1ebrates, we should prioritise areas to the north
and south of the BMC. To maintain the process of adaptive divergence, we should
ensure that maximum diversity of vegetation communities are protected within
each area. A more detailed analysis (Moritz and McDonald, in press) using the
quantitative approach described by Moritz and Faith (1998) identified as key areas
for protecting historical diversity the Finnegan Uplands to the north, the Atherton
Uplands to the south and the geographically intermediate Malbon Thompson range
(Fig. 2). By contrast, analyses of patterns of complementarity of endemic species of
vertebrate across the same area identified a different set of priority areas, the northern Thornton and Carbine Uplands and the Bellenden Ker Range, in particular
(Moritz and McDonald, in press; Fig. 2). This illustrates that genetic and species
components of diversity are not equivalent, presumably because of distinct determinants operating on different spatial and temporal scales. Both should be considered in conservation planning. However, once the set of areas that adequately
capture both species and (historical) genetic diversity are identified, the notion that
habitat heterogeneity should be maximised within areas is consistent with both
maintaining adaptive diversity and maximising the diversity of species (Williams
1997; Williams and Pearson 1997) and ecosystems.