Synthesis
119
According to Korfiatis and Stamou, (submitted), the most important feature of habitat templets is their capability to describe different mechanisms of
causality than the r-K selection model. In fact, unlike the r-K selection model
in which density dependence is the driving selective force, the principal factor
causing selection in habitat templets relates to elements of the physical environment such as stress, disturbance, favourability and predictability. Habitat
templets have strongly influenced experimental and theoretical work. A population-into-its-environment thinking overwhelms research in the 1990s, and
in the experimental and theoretical work habitats and organisms are viewed
as parts of a feedback-linked system (Korfiatis and Stamou, submitted). For
example, Southwood (1977) stated that the features of an organism interact
with the habitat through an adopted strategy, and organism-environment
relationships are considered as a multivariate-multilevel phenomenon, while
life-history strategies are viewed as a complex of interacting characteristics.
Methodological changes have been considerable. Instead of only demographic parameters, habitat-templet studies involve trade-offs between physiological processes, mechanisms of predator avoidance, ontogenetic processes, such as somatic growth, reproductive tactics, dispersal, diapause etc.
(Southwood 1988).
Despite some advantages, the use of habitat templets is rather limited. To a
great extent this is due to ambiguities concerning the exact definition of concepts as well as to misunderstandings. An example of such difficulties is the
concept of quiescence in oribatids, i.e. the temporary halting of development
below certain temperature thresholds. Indeed, irrespective of whether it is a
recently developed apotypic adaptation in response to actual selective forces
or a realisation of temperature and/or humidity dependent on ancestral
metabolic constraints, quiescence coupled with immediate and left-skewed
metabolic response to increasing temperature is of primordial importance
for Mediterranean arthropods. In fact, it allows animals to overcome hazardous (in autumn and spring) and normally occurring (in winter) low temperatures, while quiescence coupled with rapid response to changing temperature
also enables animals to exploit the slightest temperature increases to accomplish parts of their life cycle development in winter. Apparently, the consideration of various life history attributes within a life history context assigns to
them precise adaptive values, irrespective of their origin. Moreover, several
life history traits may equally be elements of different life history strategies.
For example, Siepel (1994) stated that, although phoresy is normally considered as an r-strategy attribute allowing arthropods the rapid colonisation
of either ephemeral or discretely distributed biotopes, it characterises mesostigmatic species showing for the most part K-strategy features.
In the following paragraphs, an attempt to discuss adaptations of Mediterranean arthropods will be undertaken within a habitat templet context as
outlined above. The problem can be stated as follows: as shown in Chapter 7,
specific Mediterranean faunas have not been described and most Mediterra-
119
According to Korfiatis and Stamou, (submitted), the most important feature of habitat templets is their capability to describe different mechanisms of
causality than the r-K selection model. In fact, unlike the r-K selection model
in which density dependence is the driving selective force, the principal factor
causing selection in habitat templets relates to elements of the physical environment such as stress, disturbance, favourability and predictability. Habitat
templets have strongly influenced experimental and theoretical work. A population-into-its-environment thinking overwhelms research in the 1990s, and
in the experimental and theoretical work habitats and organisms are viewed
as parts of a feedback-linked system (Korfiatis and Stamou, submitted). For
example, Southwood (1977) stated that the features of an organism interact
with the habitat through an adopted strategy, and organism-environment
relationships are considered as a multivariate-multilevel phenomenon, while
life-history strategies are viewed as a complex of interacting characteristics.
Methodological changes have been considerable. Instead of only demographic parameters, habitat-templet studies involve trade-offs between physiological processes, mechanisms of predator avoidance, ontogenetic processes, such as somatic growth, reproductive tactics, dispersal, diapause etc.
(Southwood 1988).
Despite some advantages, the use of habitat templets is rather limited. To a
great extent this is due to ambiguities concerning the exact definition of concepts as well as to misunderstandings. An example of such difficulties is the
concept of quiescence in oribatids, i.e. the temporary halting of development
below certain temperature thresholds. Indeed, irrespective of whether it is a
recently developed apotypic adaptation in response to actual selective forces
or a realisation of temperature and/or humidity dependent on ancestral
metabolic constraints, quiescence coupled with immediate and left-skewed
metabolic response to increasing temperature is of primordial importance
for Mediterranean arthropods. In fact, it allows animals to overcome hazardous (in autumn and spring) and normally occurring (in winter) low temperatures, while quiescence coupled with rapid response to changing temperature
also enables animals to exploit the slightest temperature increases to accomplish parts of their life cycle development in winter. Apparently, the consideration of various life history attributes within a life history context assigns to
them precise adaptive values, irrespective of their origin. Moreover, several
life history traits may equally be elements of different life history strategies.
For example, Siepel (1994) stated that, although phoresy is normally considered as an r-strategy attribute allowing arthropods the rapid colonisation
of either ephemeral or discretely distributed biotopes, it characterises mesostigmatic species showing for the most part K-strategy features.
In the following paragraphs, an attempt to discuss adaptations of Mediterranean arthropods will be undertaken within a habitat templet context as
outlined above. The problem can be stated as follows: as shown in Chapter 7,
specific Mediterranean faunas have not been described and most Mediterra-