of western and eastern Atlantic coasts but prior to closure of the Isthmus of
Panama.
The same analyses performed on species presence-absence data can be seen in
Fig. 16.14 for the Atlantic regions and Fig. 16.15 for Pacific and Atlantic Regions.
The figure includes only species fitting more than 50 % of the axis and weighting
more than 50 %.
As previously mentioned, the affinities between faunas are a consequence of the
combination of climatic and trophic factors, connectivity as a function of distance,
current patterns and historical processes. The partition of the variance to see the
relative influence of environmental variables and spatial organization (latitude and
longitude coordinates) was done following the methodology proposed by Borcard
et al. (1992). It shows that the covariation of space and environment reach 62.2 %
in the case of Atlantic provinces. The environmental variables alone are responsible for 37.8 % of the variance. The covariation of space and environment of the
Atlantic and Pacific regions analyzed together account for only 11.4 % of the
variability while environmental variables explain 58.6 % of the variability. There
is 14.5 % variation that is purely spatial and an additional 15.5 % is of unexplained variation and stochastic fluctuations or due to historical processes linked to
the isolation of the faunas of the Caribbean and tropical Pacific after the closure of
the isthmus of Panama.
Furthermore, different environmental factors would be responsible for faunal
composition and species distribution at different spatial scales (Barry and Dayton
1991; Levin 1992; Pérez-Ruzafa et al. 2003; Entrambasaguas et al. 2008). Water
temperature is considered the most important influence on the global distribution
of marine animals and minimum temperature is usually the factor that determines
faunal similarities at small geographical scales (Steele 1983; Pérez-Ruzafa and
López-Ibor 1988; Pérez-Ruzafa et al. 2003). Factors such as predation (Tegner and
Dayton 1981; Sala 1997), settlement and recruitment (Young and Chia 1982; Ebert
1983; Hereu et al. 2004; Hernández et al. 2010), availability of trophic resources
(Menge 1992), disease epidemics (Hagen 1999; Dumont et al. 2004), or competitive interactions (Hagen and Mann 1992), physical factors like substrate nature, bottom complexity, depth, wave exposition, etc. (Drouin et al. 1985; Tyler
et al. 2000; Entrambasaguas et al. 2008) or harvesting (Pfister and Bradbury 1996;
Hasan 2005) are of major importance in explaining small scale species distribution
and abundance.
16.4 Bathymetrical and Substrate Distribution
In the Pacific taxonomic list (see appendix) there were 620 species of echinoderms
with bathymetric information (Fig. 16.16) that represent 86 % of the species of the
list, while in the Caribbean and Atlantic taxonomic list (see appendix) there were
836 species, that represent 92 % of the species on the list (Fig. 16.17). In the
Pacific most species were reported at depths between 20 and 200 m (336 species),
538
A. Pérez-Ruzafa et al.
Panama.
The same analyses performed on species presence-absence data can be seen in
Fig. 16.14 for the Atlantic regions and Fig. 16.15 for Pacific and Atlantic Regions.
The figure includes only species fitting more than 50 % of the axis and weighting
more than 50 %.
As previously mentioned, the affinities between faunas are a consequence of the
combination of climatic and trophic factors, connectivity as a function of distance,
current patterns and historical processes. The partition of the variance to see the
relative influence of environmental variables and spatial organization (latitude and
longitude coordinates) was done following the methodology proposed by Borcard
et al. (1992). It shows that the covariation of space and environment reach 62.2 %
in the case of Atlantic provinces. The environmental variables alone are responsible for 37.8 % of the variance. The covariation of space and environment of the
Atlantic and Pacific regions analyzed together account for only 11.4 % of the
variability while environmental variables explain 58.6 % of the variability. There
is 14.5 % variation that is purely spatial and an additional 15.5 % is of unexplained variation and stochastic fluctuations or due to historical processes linked to
the isolation of the faunas of the Caribbean and tropical Pacific after the closure of
the isthmus of Panama.
Furthermore, different environmental factors would be responsible for faunal
composition and species distribution at different spatial scales (Barry and Dayton
1991; Levin 1992; Pérez-Ruzafa et al. 2003; Entrambasaguas et al. 2008). Water
temperature is considered the most important influence on the global distribution
of marine animals and minimum temperature is usually the factor that determines
faunal similarities at small geographical scales (Steele 1983; Pérez-Ruzafa and
López-Ibor 1988; Pérez-Ruzafa et al. 2003). Factors such as predation (Tegner and
Dayton 1981; Sala 1997), settlement and recruitment (Young and Chia 1982; Ebert
1983; Hereu et al. 2004; Hernández et al. 2010), availability of trophic resources
(Menge 1992), disease epidemics (Hagen 1999; Dumont et al. 2004), or competitive interactions (Hagen and Mann 1992), physical factors like substrate nature, bottom complexity, depth, wave exposition, etc. (Drouin et al. 1985; Tyler
et al. 2000; Entrambasaguas et al. 2008) or harvesting (Pfister and Bradbury 1996;
Hasan 2005) are of major importance in explaining small scale species distribution
and abundance.
16.4 Bathymetrical and Substrate Distribution
In the Pacific taxonomic list (see appendix) there were 620 species of echinoderms
with bathymetric information (Fig. 16.16) that represent 86 % of the species of the
list, while in the Caribbean and Atlantic taxonomic list (see appendix) there were
836 species, that represent 92 % of the species on the list (Fig. 16.17). In the
Pacific most species were reported at depths between 20 and 200 m (336 species),
538
A. Pérez-Ruzafa et al.