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| 2. |
- Sundberg, P, et al.
(författare)
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Homoplasy, character function and nemertean systematics
- 1994
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 234:2, s. 253-263
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Tidskriftsartikel (refereegranskat)abstract
- We question recent claims that cladistic analysis is inapplicable in nemerteans (phylum Nemertea) due to a supposedly high degree of convergence. We further argue that terms like convergence and parallelism are historical sayings and only make sense in a phylogenetic context. Therefore, an approach aiming to produce phylogenetic hypotheses cannot be rejected on the grounds of a high degree of convergence before the actual hypothesis. Convergence is not an empirical observation, but a conclusion made after an analysis. We also discuss the view that knowledge of a character's function is a prerequisite for phylogenetic analysis and conclude that this is an invalid approach. Function, like any other way of sharpening our observations, helps in formulating non-phylogenetic hypotheses of homology, but the crucial test is congruence with other characters on a phylogeny.
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| 3. |
- Eriksen, B, et al.
(författare)
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Reproductive strategies in two arctic Pedicularis species (Scrophulariaceae)
- 1993
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 16:2, s. 154-166
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Tidskriftsartikel (refereegranskat)abstract
- A study of a number of reproductive traits in two sympatric species of Pedicularis in northern Swedish Lapland, the subarctic-alpine P lapponica and the artic P hursuta, revealed that the life-history strategies of the two species differ profoundly High fruit set and low seed abortion rate, as m P hursuta, is common in arctic plants in late-thawing habitats and represents a case of extreme adversity selection rather than an indication of a ruderal life-history strategy Pedicularis lapponica, on the other hand, is a typical K-strategist (or stress-tolerator) requiring a longer period of growth for optimal reproduction Occuring at both low and high altitudes in the area, P lapponica tends to increase in self-compatibility with altitude, which is interpreted as an adaptation to lower pollinator visitation frequency in arctic environments The variation in length of the protruding part of the style in P lapponica is shown to be correlated with exposure to light Predispersal seed predation is severe m P lapponica at low altitudes, where the capsules are attacked by fly and moth larvae At high altitudes, a minor proportion of the capsules of P lapponica experience predation and only from flies, while P hursuta is completely unpredated
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| 4. |
- Svensson, Mikael
(författare)
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Morphological variation in the palaeonemertean Tubulanus annulatus (Montagu, 1804)
- 1993
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 266, s. 239-246
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies on the palaeonemertean Tubulanus annulatus have hinted on possible geographic variation, or even a species complex. This study describes the variation in morphology, focusing on the characters that have been supposed to vary geographically. Specimens from the Swedish west coast (Tjärnö and Kristineberg), Scottish west coast (Millport), and the Mediterranean (Naples and Split) were included in the study. It is concluded that the pattern of variation in the studied characters do not correspond to geography and most of the character states previously thought to vary geographically are in fact found within one and the same population.
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