Source
Trappes (2021), LIT-169 (Biology & Philosophy 36:31), read in full in NOTE-155.
What was actually shown
The two concepts. The evolutionary niche is “the sum of all the natural selection pressures to which the population is exposed” (Odling-Smee, Laland & Feldman 2003:40). Read externally, it is the environmental factors that, given the phenotypes present, lead to fitness differences in a population (pp. 8–9). The ecological niche is “the environmental conditions, both biotic and abiotic, that permit the continued existence of an individual, population or species” (p. 6).
Three gaps, two closed by restriction (pp. 7–9). They differ in reference unit (population only, against individual, population or species), in modality (actual, against fundamental or realized), and in effect (fitness differences, against persistence). Restricting the ecological niche to the realized population niche closes the first two. The modality gap alone already contradicts the 2003 book’s claim that its niche translates the fundamental niche (p. 8).
The third gap does not close (p. 9). With no migration, a population persists when its average absolute fitness is at least 1 over generations. A selection pressure exists when there are fitness differences. Neither implies the other. The reading grades this step, and the non-identity it yields, strong (NOTE-155, C2 and C6).
Three kinds of non-coincidence (pp. 10–14).
- Habitat degradation: in the evolutionary niche, not the ecological one. Snow geese overgrazing Hudson Bay salt marshes; depleted resources select, while the degraded habitat “likely” no longer permits persistence. This is OLF’s own negative niche construction.
- Commensalism: in the ecological niche, not the evolutionary one. Tupiocoris notatus on Datura wrightii has no fitness effect and no interaction effect (Hare & Elle 2002), assuming no unmeasured interactions. The author’s first candidate, the same bug on Nicotiana attenuata, failed: there it primes defences and so selects.
- Non-limiting resources: atmospheric CO2 for land plants, offered as a “possible example” on a between-lineage difference. Direct evidence is “difficult to locate”.
What could have come out otherwise. Selection and persistence could have been tied by definition, or every candidate case could have failed as the first commensal did. The first did not happen; the second nearly did.
What this does not say
- That the two niches differ much. They “still coincide to a large extent” (p. 15), and the size of the non-coincidence is not measured.
- That niche construction theory as a whole uses this niche. Only the 2003 book is analysed. Later concepts (Stotz 2017’s selective and developmental niches; constitutive and relational niche construction) are set aside, and the author says so.
- That a phenotype-inclusive evolutionary niche would differ as much. The result rests on the externalist reading of selection pressure, which the paper calls “standard, though contested”. A niche that includes phenotypic change “may” show greater similarity (p. 9).
- That each case is established. Two of the three rest on a single study or a hypothetical. The non-identity does not depend on them; the claim that real systems fall in the gap does.
- That niche construction has no evolutionary significance. The conclusion is that its significance “would not be a given”: it is to be shown case by case, not read off the definition (pp. 16–17).
Connections
- Takola & Schielzeth, LIT-127, build an individualized ecological niche with a persistence-style criterion (expected lifetime reproductive success at least 1). Trappes sets individual niches aside and asks whether an individualized evolutionary niche could be defined. LIT-127 answers only the ecological half.
- Baedke et al., LIT-110, from the same research network, analyse the causal structure of niche construction; this paper analyses its object.