CHAPTER 51
Biodiversity at Ecogenetic Level in Three Species of Beach Fleas
L. Zane, E. Angelini, N. Longo, S. Marcato, and P.M. Bisol
ABSTRACT
Patterns of fine-scale niche diversification were investigated in three co-generic species of littoral
amphipods. Population samples of Orchestia montagui, O. gammarella and O. mediterranea were
collected from the same sampling sitel in the Venice Lagoon, and analysed by means of protein
electrophoresis and RAPD techniques. The three species exhibited significant differences at the
protein and the nuclear DNA level. Specific markers were identified that allow the correct species
assignment of females, that are morphologically indistinguishable. Two species, O. montagui, that
occurs under vegetal debris, and O.mediterranea, found on muddy infra-littoral substrates, were
further investigated with regard to the resistance to high temperature and to glucose-phosphate
isomerase (GPI) biochemical activity. The two species were found to have different resistance to
high temperatures, with O. montagui showing the higher survival rate. The thermal stability of
the common GPI genotype and the biochemical activity of this enzyme was higher in O. montagui. Our results strongly suggest that a relationship exists between habitat preference and
metabolic properties that can explain the competition avoidance in these animals.
Introduction
The preservation of biological diversity has
become an increasingly important issue in recent
years. The number of endangered species is rapidly growing, due to several factors including
habitat loss, introduction of allocthonous
species, overexploitation, and pollution. Several
reasons have been proposed to justify the preservation of biodiversity including the economic
value of bioresources, ecosystem services, aesthetics and the right of living organisms to exist
(reviewed in Frankham 1995; OECD 1996).
The World Conservation Union (IUCN) now
recognizes the need to maintain biodiversity at
three levels: genetic diversity, species diversity,
and ecosystem diversity (World Conservation
Monitoring Centre 1992). These indications
result from the importance of preserving the different functional units together with the habitat
in which they live.
Under this regard, the preservation of functionality of lagoons is of particular importance
due to their high economical and ecological
value. Among others) these habitats often sustain
anthropic activities with high productivity like
local fisheries and mollusc harvest industries,
and are an important feeding ground for migratory birds.
Moreover, like other transition zones)
lagoons are particularly important because they
represent natural laboratories for the study of
adaptive processes (Battaglia and Bisol 1988).
Due to the strong temporal variation in environmental parameters such as salinity and temperature, organisms that inhabit these areas show
peculiar specializations that enable them to tackle strong selective pressures.
The present study deals with the assessment
of genetic and functional diversity in three talitrid species, Orchestia montagui, O. gammarella
and O. mediterranea from a littoral lagoon area.
Talitrids are, with isopods, the only crustaceans
which were able to colonize a terrestrial habitat;
this colonization is thought to date to the upper
Cretaceous (70 million years ago), and was
accompanied by an extensive radiation. which
led talitrids to fill all the ecological niches they
Dipartimento di Biologia, UniversitA degli Studi di Padova, Via Ugo Bassi 58tH, 35121 Padova, Italy
F.M. Faranda, L. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Processes
@ Springer-Verlag Italia 2001
Biodiversity at Ecogenetic Level in Three Species of Beach Fleas
L. Zane, E. Angelini, N. Longo, S. Marcato, and P.M. Bisol
ABSTRACT
Patterns of fine-scale niche diversification were investigated in three co-generic species of littoral
amphipods. Population samples of Orchestia montagui, O. gammarella and O. mediterranea were
collected from the same sampling sitel in the Venice Lagoon, and analysed by means of protein
electrophoresis and RAPD techniques. The three species exhibited significant differences at the
protein and the nuclear DNA level. Specific markers were identified that allow the correct species
assignment of females, that are morphologically indistinguishable. Two species, O. montagui, that
occurs under vegetal debris, and O.mediterranea, found on muddy infra-littoral substrates, were
further investigated with regard to the resistance to high temperature and to glucose-phosphate
isomerase (GPI) biochemical activity. The two species were found to have different resistance to
high temperatures, with O. montagui showing the higher survival rate. The thermal stability of
the common GPI genotype and the biochemical activity of this enzyme was higher in O. montagui. Our results strongly suggest that a relationship exists between habitat preference and
metabolic properties that can explain the competition avoidance in these animals.
Introduction
The preservation of biological diversity has
become an increasingly important issue in recent
years. The number of endangered species is rapidly growing, due to several factors including
habitat loss, introduction of allocthonous
species, overexploitation, and pollution. Several
reasons have been proposed to justify the preservation of biodiversity including the economic
value of bioresources, ecosystem services, aesthetics and the right of living organisms to exist
(reviewed in Frankham 1995; OECD 1996).
The World Conservation Union (IUCN) now
recognizes the need to maintain biodiversity at
three levels: genetic diversity, species diversity,
and ecosystem diversity (World Conservation
Monitoring Centre 1992). These indications
result from the importance of preserving the different functional units together with the habitat
in which they live.
Under this regard, the preservation of functionality of lagoons is of particular importance
due to their high economical and ecological
value. Among others) these habitats often sustain
anthropic activities with high productivity like
local fisheries and mollusc harvest industries,
and are an important feeding ground for migratory birds.
Moreover, like other transition zones)
lagoons are particularly important because they
represent natural laboratories for the study of
adaptive processes (Battaglia and Bisol 1988).
Due to the strong temporal variation in environmental parameters such as salinity and temperature, organisms that inhabit these areas show
peculiar specializations that enable them to tackle strong selective pressures.
The present study deals with the assessment
of genetic and functional diversity in three talitrid species, Orchestia montagui, O. gammarella
and O. mediterranea from a littoral lagoon area.
Talitrids are, with isopods, the only crustaceans
which were able to colonize a terrestrial habitat;
this colonization is thought to date to the upper
Cretaceous (70 million years ago), and was
accompanied by an extensive radiation. which
led talitrids to fill all the ecological niches they
Dipartimento di Biologia, UniversitA degli Studi di Padova, Via Ugo Bassi 58tH, 35121 Padova, Italy
F.M. Faranda, L. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Processes
@ Springer-Verlag Italia 2001