Palaeontologia Electronica palaeo-electronica.org What are the best modern analogs for ancient South American mammal communities? Evidence from ecological diversity analysis (EDA) Angeline M. Catena and Darin A. Croft ABSTRACT Ecological diversity analysis (EDA) is a technique that uses ecological attributes of mammals to reconstruct the community structure and habitat of a fossil locality. EDAs of South American paleofaunas have generally relied on modern comparative datasets from that continent, but modern faunas from other continents may be more appropriate models considering the high-level taxonomic differences that exist between modern and fossil South American mammal communities. To test this hypoth- esis, we selected five, well-sampled fossil localities for which independent paleoenvi- ronmental data (e.g., paleosols, ichnofossils) have been published: four from South America (La Venta, Colombia; Quebrada Honda, Bolivia; Santa Cruz, Argentina; Tin- guiririca, Chile) and one from Europe (Rümikon, Switzerland). We coded the extinct species from these sites, as well as ca. 2,450 modern mammal species, for three eco- logical attributes: diet (eight categories), locomotor habit (six categories), and body mass (six categories). Percentages of species in each attribute category were used to compare the five paleofaunas to 179 modern faunas from six continents using corre- spondence analysis, hierarchical clustering, similarity percentage, and classification trees. The four South American paleofaunas were found to be most similar to Afrotrop- ical, Indo-Malayan, and Palearctic modern faunas and, similarly, the European paleo- fauna most resembled faunas from a biome not currently present in the Palearctic. Our study highlights important differences in community structure between ancient and modern South American mammal faunas and suggests that modern mammalian com- munities from other continents are better analogues for ancient South American com- munities than modern South American faunas. Angeline M. Catena. Diablo Valley College, 321 Golf Club Road, Pleasant Hill, California, 94523-1529, USA. [email protected] Darin A. Croft. Department of Anatomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio, 44196-4930, USA. [email protected] Catena, Angeline M. and Croft, Darin A. 2020. What are the best modern analogs for ancient South American mammal communities? Evidence from ecological diversity analysis (EDA). Palaeontologia Electronica 23(1):a03. https://doi.org/10.26879/962 palaeo-electronica.org/content/2020/2909-south-america-mammal-eda Copyright: February 2020 Society of Vertebrate Paleontology. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. creativecommons.org/licenses/by/4.0/creativecommons.org/licenses/by-nc-sa/4.0/ CATENA & CROFT: SOUTH AMERICA MAMMAL EDA Keywords: Cenozoic; Ecology; Community Structure; South America; Paleoenvironment; Neotropics Submission: 27 January 2019. Acceptance: 14 January 2020. INTRODUCTION 2012). Continental ichnology is also a relatively new field, and ichnofossils are often overlooked Paleontologists use a variety of approaches to (Voorhies, 1975; Howard, 1977; Buatois and Mán- reconstruct terrestrial habitats, climates, and eco- gano, 1995; Hembree et al., 2012). Plant macro- logical communities (Dark, 2008; Piperno, 2008; fossils and pollen are not typically preserved in the Shuman, 2009; Wright, 2017; Croft et al., 2018b). same sediments that preserve terrestrial verte- For example, sedimentological analyses can be brates, and although this is not true of phytoliths, used to determine the sources of sediments and their abundance can vary considerably depending characteristics of a depositional environment on sedimentological conditions (Solomon and Silk- (Boggs, 2006; Nichols, 2009, Wright, 2017). Pale- worth, 1986; Hjelmroos and Franzén, 1994; Janis, opedology can be used to deduce environmental 2000; Wright, 2017). In this context, ecological factors such as mean annual precipitation and diversity analysis (EDA) can be an effective alter- paleotopographic position (Caudill et al., 1996; native for reconstructing terrestrial paleoenviron- Cerling et al., 1989; Retallack, 1994; Kraus, 1999; ments, particularly for faunas that are already well Retallack, 2001; Driese and Ober, 2005; Retallack, sampled and described. EDA has the added bene- 2005; Kraus and Riggins, 2007), and ichnology can fit of providing insights into the ecological structure be used to determine soil moisture regimes, pri- of past communities. mary productivity, and shifts in ecosystems related Ecological diversity analysis is a technique to changes in environmental conditions (Rhoads, based on the concept that the ecological adapta- 1975; Retallack, 1984; Hasiotis, 2002, 2007; Kraus tions of an animal are reflected in its morphology and Riggins, 2007; Smith et al., 2008; Hembree (Losos, 1990; Saunders and Barclay, 1992; Wain- 2018). Plant fossils, including macrofossils (wood, wright and Reilly, 1994; Werdelin, 1996). Studies of leaves), pollen, and phytoliths, can provide taxo- modern mammal communities have shown that nomic and ecomorphological information pertaining proportions of mammals in different ecomorpholog- to floral communities, vegetative cover, and climate ical categories vary with habitat (Fleming, 1973; (Hooghiemstra, 1989; Wing and Greenwood, 1994; Andrews et al., 1979; Eisenberg, 1981; Brown, Gregory-Wodzicki et al., 1998; Dunn et al., 2015; 1995). Although the biological attributes of a fossil Wright 2017; Kovarovic et al., 2018; Mander and species cannot be observed directly, such attri- Punyasena, 2018; Peppe et al., 2018; Strömberg butes can be inferred with some confidence by et al., 2018). Ecological attributes and/or environ- comparing craniodental and postcranial anatomy to mental constraints of vertebrates can be used to that of modern species (Kappelmann, 1988; Scott infer properties of the environments in which they et al., 1990; DeGusta and Vrba, 2003, 2005; lived (Fleming, 1973; Andrews et al., 1979; Eisen- Kovarovic et al., 2018). By repeating this process berg, 1981; Brown, 1995; Blain et al., 2008; Fin- for all species in a fossil assemblage and compar- layson et al., 2011; Louchart et al., 2001; Cruz et ing the resulting community structure to that of al., 2016; Vermillion et al., 2018). modern faunas, the paleohabitat of a fossil site can Under ideal circumstances, all of the afore- be reconstructed (Andrews and Van Couvering, mentioned techniques can be used to create a mul- 1975; Nesbit Evans et al., 1979; Van Couvering tifaceted paleoenvironmental reconstruction of a 1980). This type of ecomorphological approach is fossil locality (Su and Croft, 2018). Unfortunately, considered to be taxon-independent because the this is seldom possible. Sedimentology has only proportions of species occupying broad ecological existed as a distinct branch of geology for several niches within a particular habitat type tend to be decades (Nichols, 2009); consequently, the sedi- similar regardless of the taxonomic affinities of the mentology (and paleopedology) of many histori- species involved (Fleming, 1973; Andrews and cally older fossil localities remain unknown or are Nesbet Evans, 1979; Andrews et al., 1979 described in insufficient detail for stand-alone Damuth, 1992). In theory, an EDA of any fauna for facies and environmental analyses (Bronger and which the ecological characteristics of its species Catt, 1989; Kraus and Bown, 1986; Retallack, can be determined should faithfully reflect the habi- 2001; Stanley, 2005; Matheos and Raigemborn, tat in which those species were living. 2 PALAEO-ELECTRONICA.ORG Ecological diversity analysis was originally 2006; Fiedel, 2009; Barnosky and Lindsey, 2010; developed and applied to late Cenozoic hominin- Villavivencio et al., 2015). These two events sub- bearing sites in Africa (e.g., Andrews and Lord, stantially changed the high-level taxonomic compo- 1979; Andrews et al., 1979; Van Couvering 1980), sition of South American mammal communities but the technique has also been used to recon- relative to modern ones, with the result that mod- struct South American paleohabitats (e.g., Kay and ern South American mammal faunas bear very lit- Madden, 1997a, b; Flynn et al., 2003; Croft et al., tle resemblance to those that predominated for 2008; Kay et al., 2012; Lintulaakso and Kovarovic, much of the Cenozoic (Croft, 2012). 2016). The study of these geologically older South Given the aforementioned differences American mammal faunas comes with a formidable between fossil and modern South American mam- set of challenges due to the continent’s biogeo- mal faunas, one might reasonably question graphic history. For the majority of the Cenozoic, whether modern South American mammal faunas South America was geographically and therefore are the best ecological analogues for South Ameri- biotically isolated from other landmasses and can paleofaunas (cf. Croft and Townsend, 2005). developed a highly endemic terrestrial mammal Even though general resemblances in community fauna (Patterson and Pascual, 1968; Fooden, structure may be sufficient for reconstructing 1972; Simpson, 1980; Marshall et al., 1983; Flynn paleohabitat (e.g., Kay and Madden, 1997a, b; and Wyss, 1998; Croft, 2016). During the Paleo- Flynn et al., 2003; Croft et al., 2008), limiting