Abstract
The quantification of lobule shape for Radula spp. shows that there is overlap in lobule shape space occupied by subgenera, such that lobule shape does not always reflect relationships. Morphological convergence caused by lineages repeatedly traversing shared regions of morphospace appears commonplace in Radula, and means that many pairs of relatively unrelated species have similar lobule shapes. When observed over time, as in comparisons between fossil and extant species, this may give the impression of stasis if fossil species resemble modern species by chance, independent of their relatedness. This poses a challenge to relating fossils of known age to extant lineages, particularly when fossils are sterile. Significant rate variation between lineages was identified by Adams' Q-mode analysis, with the fastest subgenus evolving 23 times more quickly than the slowest. Species of subgenus Volutoradula and subgenus Metaradula are apparently over-dispersed throughout lobule morphospace according to Sidlauskas' method; morphometric branch lengths and hypervolumes in other subgenera can be explained by a stochastic process. In contrast, Bayesian analysis of macroevolutionary mixtures (BAMM) identified a single evolutionary rate as having the highest posterior probability. Consideration of the three independent accessions into auriculate lobule morphospace by Cladoradula and Radula, wherein convergent lobule shapes result from convergent lobule ontogenies and are correlated with bipinnately branched shoot systems and robust primary stems, leads to an ontogenetic hypothesis driven by structural requirements for light interception, under which auriculate lobules are a spandrel. It is speculated that lobules themselves, however, may be a key innovation facilitating radiation into microsites devoid of or depauperate in fungal endophytes.
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Claims 11
Claim · model-written summary
Radula subgenera overlap in lobule shape space, so shape does not always reflect relationships.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there is overlap in lobule shape space occupied by subgenera, such that lobule shape does not always reflect relationships”
e1“Radula spp.”
Claim · model-written summary
Convergent lobule shapes are commonplace among relatively unrelated Radula species.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Morphological convergence caused by lineages repeatedly traversing shared regions of morphospace appears commonplace in Radula, and means that many pairs of relatively unrelated species have similar lobule shapes”
Claim · model-written summary
Adams Q-mode analysis found significant evolutionary rate variation, with the fastest subgenus evolving 23 times faster than the slowest.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant rate variation between lineages was identified by Adams' Q-mode analysis, with the fastest subgenus evolving 23 times more quickly than the slowest.”
e1“Radula spp.”
Claim · model-written summary
Volutoradula species were apparently over-dispersed through lobule morphospace.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Species of subgenus Volutoradula and subgenus Metaradula are apparently over-dispersed throughout lobule morphospace”
e1“Radula spp.”
Claim · model-written summary
Metaradula species were apparently over-dispersed through lobule morphospace.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Species of subgenus Volutoradula and subgenus Metaradula are apparently over-dispersed throughout lobule morphospace”
e1“Radula spp.”
Claim · model-written summary
A stochastic process could explain morphometric branch lengths and hypervolumes in other subgenera.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“morphometric branch lengths and hypervolumes in other subgenera can be explained by a stochastic process”
e1“Radula spp.”
Claim · model-written summary
BAMM assigned the highest posterior probability to a single evolutionary rate.
- Outcome
- single evolutionary rate as having the highest posterior probabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bayesian analysis of macroevolutionary mixtures (BAMM) identified a single evolutionary rate as having the highest posterior probability”
e1“Radula spp.”
Claim · model-written summary
Three independent entries into auriculate lobule morphospace occurred in Cladoradula and Radula.
- Taxon
- Cladoradula and Radula
RadulaCladoradulae0 - Outcome
- independent accessions into auriculate lobule morphospacee0
- Value
- threee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“three independent accessions into auriculate lobule morphospace by Cladoradula and Radula”
Claim · model-written summary
Convergent lobule shapes were associated with convergent ontogenies, bipinnate branching and robust primary stems.
- Taxon
- Cladoradula and RadulaRadulaCladoradulae1
- Organ / stage
- bipinnately branched shoot systems and robust primary stemse0
- Outcome
- convergent lobule shapese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“convergent lobule shapes result from convergent lobule ontogenies and are correlated with bipinnately branched shoot systems and robust primary stems”
e1“Cladoradula and Radula”
Claim · model-written summary
Auriculate lobules were hypothesized to be a spandrel of structural requirements for light interception.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ontogenetic hypothesis driven by structural requirements for light interception, under which auriculate lobules are a spandrel”
e1“Radula, wherein convergent lobule shapes”
Claim · model-written summary
Lobules were speculated to facilitate radiation into microsites lacking or poor in fungal endophytes.
- Organ / stage
- lobulese0
- Outcome
- radiation into microsites devoid of or depauperate in fungal endophytese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lobules themselves, however, may be a key innovation facilitating radiation into microsites devoid of or depauperate in fungal endophytes”
e1“Radula, wherein convergent lobule shapes”