Who is at the worst?

Salva salherra at ono.com
Tue Jul 9 15:11:27 EST 2002


Dear friends,

I have just attended a course on quantitative sampling of behaviour and 
population group structure of the common dolphin (Delphinus delphis) in the 
Ionian Sea (Greece), and this made me think on the, to a certain extain, 
different approaches we have to assess pattern in both marine vertebrate 
and invertebrates.  

I would like to present the following line of discussion:

Population patterns of whatever kind are determined by a number of 
generating mechanisms (processes) acting at different scales. However, 
only once decisions have been taken as to how to measure pattern and how 
to assess the scales of variation of the pattern measure selected, pattern 
and process can be identified and interrelated.  


Therefore, in order to account for a population pattern we face 3 factors 
operating at various scales (i.e. 3 possible sources of error in perceiving 
pattern): 1/ the scale of our sampling metthod, 2/ the scale of the natural 
history feature under study in our population, and 3/ the scale of the 
process/es affecting such feature. Most of us will be familiar with the idea 
that, in biodiversity studies, the taxonomic level of species is no less a 
classification than say that of reproductive modes. What is important is that 
classifications discriminate guilds of organisms according to a range of 
criteria (genetics, morphology, feeding, mobility,...), each of those guilds 
being potentially influenced by a distinct set of processes and therefore valid 
to answer particular ecological questions.  

In designing a quantitative study, we may well want to follow 2 rules of 
thumb: 1/ Huston (1994) suggested that experimental research should 
maximise the detection of pattern (sensu heterogeneity) while minimising the 
number of processes involved. 2/ The bigger an animal, the wider its ambit, 
the lower its density. We zoologists always complain that we work on 
estimates because we can’t (and shouldn’t) sample the whole population, 
and this obvious remark (and the implicit scientific frustration!) is perhaps 
exacerbated whether the total population amounts to millions or billions (i.e. 
polychaetes) or to hundreds or at best thousands (all aquatic vertebrates to 
my knowledge) (how unfair?: overall, do invertebrate researchers get less 
money for a harder work?!!!).  


I am currently writting a divulgative paper on the dolphin workshop referred to 
above, and would appreciate any comment or bibliographic references on 
the following question?  

Do we have any comparison between measuring quantitative patterns 
whether we are working on vertebrate or invertebrate species populations?  

In other words, are say cetologists in a better possition than benthologists 
because say in a chemical discharge causing mortality of the entire marine 
fauna they can analyse chemical contents in the bodies of a percentage of 
the total population of a dolphin species far greater than that of mostly any 
invertebrate species? I am not sure perhaps this is a purely statistical 
question.  

Cheers.

Salva

Salvador Herrando-Pérez
Biólogo, MPhil BSc
Narrador literario

DOMICILIO
C/ Padre Jofre 19,piso 3, pta 7
12006 Castellón de la Plana
ESPAÑA

Teléfonos: (34) 964 038845  / (34) 657 787340
Mail: salherra at ono.com / salherra at ctv.es / salherra at ull.es


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