Conservation planning in a changing world
221
rate of body length change was increased for both
smaller and larger mammals, while it was lower for the
medium - sized species. Following the general trend
of the island rule, small mammals have generally
increased, whereas large mammals have decreased in
length. Schmidt & Jensen suggested that the major, but
not the only, driver of these changes was habitat
fragmentation.
Based on island studies, Losos & Schluter (2000)
have identifi ed that for Anolis lizards in the Great
Antilles, below a certain island size threshold there is
little or no cladogenesis. The identifi cation of such size
thresholds not only in the short term, but over evolutionary timescales, could be quite insightful for conservation biogeography (e.g. Triantis et al. , 2008 ). This
corresponds to the plea of Gunderson & Folke (2003) ,
who called upon conservation biologists to work
towards the ‘ science of the long view ’ and to integrate
insights from other disciplines in the search for new
predictive and transcalar models in time and space (see
also Lomolino, 2006 ).
3 Assembly rules (phylogeny): Island biotas are
not simply random draws from regional species pools.
Instead, they typically exhibit compositional structure:
some species, species combinations, or species types,
are found more frequently, and some less frequently,
than might be expected by chance. This idea was presented in Jared Diamond ’ s island assembly theory
(Diamond, 1975b ; reviewed in Whittaker & Fern á ndez -
Palacios, 2007 ). Related to island assembly theory is
an increasing number of studies appearing to show
deterministic patterns of evolution on islands, i.e. independent evolutionary diversifi cation events, producing
on different islands the same set of habitat specialists
adapted to use different parts of the environment (see
Losos et al ., 1998 ; Chiba, 2004 ; Gillespie, 2004 ; Losos
& Ricklefs, 2010 ).
The incorporation of phylogenetics into community
ecology will offer key insights into the assembly and
structure of communities (see Webb et al ., 2002 ;
Emerson & Gillespie, 2008 ), with insular systems
having a pivotal contribution to make within this
research programme. Extinction and extinction risk
are often phylogenetically non - random (Purvis, 2008 ).
Nonrandomness when species are faced with a similar
threat intensity indicates that some species are more
extinction resistant than others (e.g. Purvis et al .,
2000 ). Hence the use of phylogenies for identifi cation
of those traits that are associated with a high extinction risk in declining species, e.g. high trophic level,
of habitat loss and fragmentation (Simberloff & Martin,
1991 ; Laurance 2002 ).
A highly relevant island phenomenon is the so -
called ‘ small island effect ’ (see Lomolino & Weiser,
2001 ; Triantis et al. , 2006 ). The main feature of the
phenomenon is the absence of the commonly found
relationship of island area and species richness below
a certain island size (dashed line in Figure 8.11 ). The
particular threshold of this effect appears to vary
depending on the taxon and archipelago selected, but
it generally appears to occur only with islands of a very
small size and diversity. In practice, within the limits of
the small island effect, species richness is independent
from the direct effects of area and is mainly driven by
the effects of habitat diversity. Hence, it would be interesting to assess the existence of such thresholds in
habitat island data sets for which the usual explanatory variables – such as area and isolation – are not
important (see Prugh et al. , 2008 ) and other variables
– such as island age, productivity, energy and environmental heterogeneity – are important. The consideration of such variables, although challenging, is
necessary if we are to build up a more predictive science
of species richness variation across true and habitat
island systems.
In a fragmented landscape, species can either become
extinct or go through changes in life history traits that
will adapt them to the changed living conditions.
Another issue related to spatial thresholds of fragmented landscapes that has received limited attention
is how the evolutionary dynamics of species change in
response to landscape transformation. Adaptation in a
fragmented landscape may infl uence measurable features of the phenotype of a species, e.g. body size. In
island studies, it is well established that islands favour
the change of species body size, compared to their
mainland counterparts; usually small species become
larger (gigantism) and large species smaller (nanism)
– a phenomenon termed the ‘ island rule ’ (Lomolino,
1985 ). These changes lead to a more effective exploitation of the available resources in the context of the
limited available space on islands. The absence of the
full collection of competitors and predators found on
the mainland contributes towards these size changes
(see Lomolino, 2005 ; Lomolino et al. , 2006 ; but see
Meiri et al. , 2006 ).
In illustration of these effects within a habitat island
context, Schmidt & Jensen (2003) studied the body size
changes within the entire Danish mammalian community during the last 175 years. They found that the
221
rate of body length change was increased for both
smaller and larger mammals, while it was lower for the
medium - sized species. Following the general trend
of the island rule, small mammals have generally
increased, whereas large mammals have decreased in
length. Schmidt & Jensen suggested that the major, but
not the only, driver of these changes was habitat
fragmentation.
Based on island studies, Losos & Schluter (2000)
have identifi ed that for Anolis lizards in the Great
Antilles, below a certain island size threshold there is
little or no cladogenesis. The identifi cation of such size
thresholds not only in the short term, but over evolutionary timescales, could be quite insightful for conservation biogeography (e.g. Triantis et al. , 2008 ). This
corresponds to the plea of Gunderson & Folke (2003) ,
who called upon conservation biologists to work
towards the ‘ science of the long view ’ and to integrate
insights from other disciplines in the search for new
predictive and transcalar models in time and space (see
also Lomolino, 2006 ).
3 Assembly rules (phylogeny): Island biotas are
not simply random draws from regional species pools.
Instead, they typically exhibit compositional structure:
some species, species combinations, or species types,
are found more frequently, and some less frequently,
than might be expected by chance. This idea was presented in Jared Diamond ’ s island assembly theory
(Diamond, 1975b ; reviewed in Whittaker & Fern á ndez -
Palacios, 2007 ). Related to island assembly theory is
an increasing number of studies appearing to show
deterministic patterns of evolution on islands, i.e. independent evolutionary diversifi cation events, producing
on different islands the same set of habitat specialists
adapted to use different parts of the environment (see
Losos et al ., 1998 ; Chiba, 2004 ; Gillespie, 2004 ; Losos
& Ricklefs, 2010 ).
The incorporation of phylogenetics into community
ecology will offer key insights into the assembly and
structure of communities (see Webb et al ., 2002 ;
Emerson & Gillespie, 2008 ), with insular systems
having a pivotal contribution to make within this
research programme. Extinction and extinction risk
are often phylogenetically non - random (Purvis, 2008 ).
Nonrandomness when species are faced with a similar
threat intensity indicates that some species are more
extinction resistant than others (e.g. Purvis et al .,
2000 ). Hence the use of phylogenies for identifi cation
of those traits that are associated with a high extinction risk in declining species, e.g. high trophic level,
of habitat loss and fragmentation (Simberloff & Martin,
1991 ; Laurance 2002 ).
A highly relevant island phenomenon is the so -
called ‘ small island effect ’ (see Lomolino & Weiser,
2001 ; Triantis et al. , 2006 ). The main feature of the
phenomenon is the absence of the commonly found
relationship of island area and species richness below
a certain island size (dashed line in Figure 8.11 ). The
particular threshold of this effect appears to vary
depending on the taxon and archipelago selected, but
it generally appears to occur only with islands of a very
small size and diversity. In practice, within the limits of
the small island effect, species richness is independent
from the direct effects of area and is mainly driven by
the effects of habitat diversity. Hence, it would be interesting to assess the existence of such thresholds in
habitat island data sets for which the usual explanatory variables – such as area and isolation – are not
important (see Prugh et al. , 2008 ) and other variables
– such as island age, productivity, energy and environmental heterogeneity – are important. The consideration of such variables, although challenging, is
necessary if we are to build up a more predictive science
of species richness variation across true and habitat
island systems.
In a fragmented landscape, species can either become
extinct or go through changes in life history traits that
will adapt them to the changed living conditions.
Another issue related to spatial thresholds of fragmented landscapes that has received limited attention
is how the evolutionary dynamics of species change in
response to landscape transformation. Adaptation in a
fragmented landscape may infl uence measurable features of the phenotype of a species, e.g. body size. In
island studies, it is well established that islands favour
the change of species body size, compared to their
mainland counterparts; usually small species become
larger (gigantism) and large species smaller (nanism)
– a phenomenon termed the ‘ island rule ’ (Lomolino,
1985 ). These changes lead to a more effective exploitation of the available resources in the context of the
limited available space on islands. The absence of the
full collection of competitors and predators found on
the mainland contributes towards these size changes
(see Lomolino, 2005 ; Lomolino et al. , 2006 ; but see
Meiri et al. , 2006 ).
In illustration of these effects within a habitat island
context, Schmidt & Jensen (2003) studied the body size
changes within the entire Danish mammalian community during the last 175 years. They found that the