title: Negative density-distribution relationship in butterflies.
abstract: BACKGROUND
  Because "laws of nature" do not exist in ecology, much of the foundations of community ecology rely on broad statistical generalisations. One of the strongest generalisations is the positive relationship between density and distribution within a given taxonomic assemblage; that is, locally abundant species are more widespread than locally sparse species. Several mechanisms have been proposed to create this positive relationship, and the testing of these mechanisms is attracting increasing attention.
  
  
  RESULTS
  We report a strong, but counterintuitive, negative relationship between density and distribution in the butterfly fauna of Finland. With an exceptionally comprehensive data set (data includes all 95 resident species in Finland and over 1.5 million individuals), we have been able to submit several of the mechanisms to powerful direct empirical testing. Without exception, we failed to find evidence for the proposed mechanisms creating a positive density-distribution relationship. On the contrary, we found that many of the mechanisms are equally able to generate a negative relationship.
  
  
  CONCLUSIONS
  We suggest that one important determinant of density-distribution relationships is the geographical location of the study: on the edge of a distribution range, suitable habitat patches are likely to be more isolated than in the core of the range. In such a situation, only the largest and best quality patches are likely to be occupied, and these by definition can support a relatively dense population leading to a negative density-distribution relationship. Finally, we conclude that generalizations about the positive density-distribution relationship should be made more cautiously.
authors.affiliation: Metsähallitus, Natural Heritage Services, P.O. Box 36, 40101 Jyväskylä, Finland. jussi.paivinen@metsa.fi <jussi.paivinen@metsa.fi>
authors.forename: Jussi
authors.initials: J
authors.lastname: Päivinen
authors.forename: Alessandro
authors.initials: A
authors.lastname: Grapputo
authors.forename: Veijo
authors.initials: V
authors.lastname: Kaitala
authors.forename: Atte
authors.initials: A
authors.lastname: Komonen
authors.forename: Janne S
authors.initials: JS
authors.lastname: Kotiaho
authors.forename: Kimmo
authors.initials: K
authors.lastname: Saarinen
authors.forename: Niklas
authors.initials: N
authors.lastname: Wahlberg
mesh_terms: D000818:Animals; D002080:Butterflies / Q000235:genetics*; D004777:Environment; D010802:Phylogeny; D011156:Population Density; D013045:Species Specificity
references.citation: Oecologia. 1980 Jan;47(2):239-251
references.pmid: 28309478
references.citation: Trends Ecol Evol. 1993 Nov;8(11):409-13
references.pmid: 21236213
references.citation: Am Nat. 2002 Dec;160(6):712-26
references.pmid: 18707460
references.citation: J Anim Ecol. 1998 Nov;67(6):995-9
references.pmid: 26412379
references.citation: J Anim Ecol. 1998 Nov;67(6):992-4
references.pmid: 26412378
references.citation: Cladistics. 2000 Dec;16(4):347-363
references.pmid: 34902900
references.citation: Oecologia. 1987 Dec;74(2):161-173
references.pmid: 28311987
references.citation: Comput Appl Biosci. 1995 Jun;11(3):247-51
references.pmid: 7583692
references.citation: Syst Biol. 2001 Feb;50(1):106-27
references.pmid: 12116588
references.citation: Oecologia. 1990 Apr;82(4):567-568
references.pmid: 28311484
references.citation: Mol Phylogenet Evol. 2003 Sep;28(3):473-84
references.pmid: 12927132
references.citation: Mol Phylogenet Evol. 2000 Apr;15(1):70-82
references.pmid: 10764536