IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Phylogenetic signal of body size in sloths and anteaters (Xenarthra, Pilosa)
Autor/es:
TOLEDO, N.; BARGO, M. S.; VIZCAÍNO, S. F.; PUJOS, F.; DE IULIIS, G.
Lugar:
Mendoza
Reunión:
Congreso; 4th International Palaeontological Congress; 2014
Institución organizadora:
IPA
Resumen:
Pilosa
xenarthrans includes sloths (Folivora) and anteaters (Vermilingua).
Modern tree sloths are represented by two genera, Bradypus
and Choloepus
(less
than 10 kg),
while the fossil record is very diverse and rich (~ 80 genera)
ranging from the Oligocene to the Early Holocene periods. The fossil
group includes four main clades, Megalonychidae, Megatheriidae,
Nothrotheriidae, and Mylodontidae, with body sizes from tens of kg to
several tons. Vermilinguans are represented today by three genera,
Cyclopes,
Tamandua,
and Myrmecophaga
(from 0.5 to about 35 kg), and their fossil record is quite scarce
and fragmentary but maybe similarly in size. we analyzed in this
contribution the dependency of the body size from the phylogenetical
pattern of Pilosa, following the current cladistic hypotheses using
previously published body size estimates for 35 taxa (extant and
extinct). An orthonormal decomposition analysis of the variance of
body size is also performed. The observed distribution of this
variable in the cladograms is compared using four statistical
parameters, with a theoretical random distribution as
null-hypothesis. Three of the four parameters were significantly
different from the null-hypothesis, supporting the possibility that
body size variation correlates with the cladograms topologies and,
hence, with the phylogenetical pattern. This dependence is not
restricted to a single node, but it is that was called diffuse
phylogenetic signal.Inthefirstcladogram,mostofthephylogeneticsignalisconcentratedwithinVermilingua,andmuchlesswithinMylodontidae,MegatheriidaeandNothrotheriidae.Inthesecondcladogram,agreatproportionofphylogeneticalsignalisconcentratedinMegatheria,andlessinMegalonychidae.Inanteaters,arelationshipbetweendietand
phylogeneticconstraintstobodysize'sdiversification
is proposed;theirspecialized,strictinsectivorymayhaveplayedaleadrolerestrainingtheevolutionofbodysize.Concerningsloths,thetrendisnotclearlyrelatedtoasinglefactor.Mylodontidsandmegatheriansshowatendencytoincreasebodysizethroughtime,whileMegalonychidaeretainawiderdiversityinbodysizeuntiltheearlyHolocene.Biologicalattributessuchasdietaryhabits(herbivorousbulkfeedingvs.selectivefeeding)andpaleoenvironmentalfactorssuchasclimatechangesthroughouttheCenozoicaredoubtlesslyinvolvedintheevolutionof
sloth's bodysize.Nextstepswillbetousealternativemethodstoassessphylogeneticdependencyandmoreaccuratebodysizeestimates.Whenavailable,moreinclusivephylogeneticalproposalscouldbenecessary,allowingexpandingtheanalysistoagreaterdiversity.