Ana Rosa Gómez Cano
I am interested in the use of mammals for palaeoenvironmental inference. The focus of my research has been in the influence of ecological redundancy on the community structure of mammalian faunas, with emphasis on the study of the redundancy pattern at the global scale.
Currently, I am studying new methods to translate morphological information from rodent teeth into ecological information that can be used for palaeoenvironmental interpretations of past communities. We want to implement such techniques in the rich succesions of mammalian fossil sites from the Iberian Peninsula.
CURRENT RESEARCH
Iberian Late Miocene paleoclimatology
Neogene mammal paleoecology
Community-climate relationships in mammal faunas
Relationships between climatic changes and evolution of mammals
More info: http://pmmv.com.es/en/node/143
Supervisors: Manuel Hernández Fernández, María Ángeles Álvarez-Sierra, and Laurent Viriot
Address: argomezcano@gmail.com
Departamento de Paleontología
Facultad de Ciencias Geológicas
Universidad Complutense de Madrid
C/ José Antonio Novais, 2
28040 Madrid (Spain)
Currently, I am studying new methods to translate morphological information from rodent teeth into ecological information that can be used for palaeoenvironmental interpretations of past communities. We want to implement such techniques in the rich succesions of mammalian fossil sites from the Iberian Peninsula.
CURRENT RESEARCH
Iberian Late Miocene paleoclimatology
Neogene mammal paleoecology
Community-climate relationships in mammal faunas
Relationships between climatic changes and evolution of mammals
More info: http://pmmv.com.es/en/node/143
Supervisors: Manuel Hernández Fernández, María Ángeles Álvarez-Sierra, and Laurent Viriot
Address: argomezcano@gmail.com
Departamento de Paleontología
Facultad de Ciencias Geológicas
Universidad Complutense de Madrid
C/ José Antonio Novais, 2
28040 Madrid (Spain)
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Papers by Ana Rosa Gómez Cano
Debris-flow hosted assemblages dominated by mammalian remains are very scarce in the fossil record and few examples are reported. Herein we present a detailed taphonomic study of Somosaguas-North (Madrid Basin, Spain), a Middle Miocene mammalian-dominated site embedded in debris flow deposits, in order to increase our knowledge of the mode of formation of fossiliferous assemblages in this depositional context. The assemblage includes 6592 large-mammal remains belonging to at least 10 different species. Fossils are found in matrix-supported, poorly-sorted coarse arkosic sandstones and fine conglomerates, which are interpreted as the result of successive debris-flow deposits. Breakage constitutes a pervasive taphonomic alteration in the bone assemblage; however, together with unidentifiable bone fragments, we also found complete to almost complete skeletal elements. Bone remains are isolated, a fact that is indicative of a time of exposure of the carcasses long enough to enable decay and complete disarticulation. There are no associations of elements belonging to the same individual, which suggests that, prior to or during debris-flow transport, bones were profusely dispersed. Based on the taphonomic evidence, we suggest that Somosaguas-North assemblage was formed by successive debris-flow transport and burial of pre-existing thanatocoenoses. Bones from those thanatocoenoses were modified by biostratinomic agents (trampling, weathering) in varying degrees depending on their time of exposure. Debris-flow transport produced further abrasion and breakage in collagen-depleted bones. Our results are congruent with an environmental context of semiarid landscapes presenting long arid periods and highly irregular hydrological seasonality. Finally, we compared the Somosaguas-North assemblage with other debris-flow hosted vertebrate assemblages. Although Somosaguas-North shares taphonomic features with some of these sites, it is not possible to define consistent and single taphonomic patterns for debris-flow assemblages, given the varied taphonomic histories of the remains prior to and during debris-flow transport.
forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different
biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas
with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a
fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the
Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are
generalists in the southern province and specialists of forested habitats in the northern province. Finally, we
identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the
Miocene. These three broad ecological groups showed differential responses to a complex set of
interconnected circumstances, including the biogeographic structure of the study area and climatic changes
throughout time.
The effect of climate change on extant mammal faunas is a frequent topic in ecological research and the analysis of past mammalian communities and their correlated evolution with global climatic change can provide data relevant to this question. Late Pleistocene and Holocene carnivore mammal faunas from the Rancho La Brea Tar Pits (Los Angeles, CA) are highly diverse and well-preserved, and were used to analyze how past climatic shifts shaped the structure of mammalian communities from southwestern North America over the past 30,000 years. Using bibliographical data, we clustered all extant terrestrial carnivores in 11 Carnivore Functional Groups with similar ecological features (diet, locomotion, and body size), and subsequently defined the functional spectra of 26 modern localities from the Nearctic. By means of discriminant analysis, we explored how the ecological structure (functional spectrum) of these communities varies with environmental conditions (type of biome). Morphofunctional analyses of La Brea species allowed us to determine their ecological features and thereby define the functional spectra of communities at different stages (pits). The selected pits varied in age: Pit 91 (around 29 ka), Pit 3 (around 18.5 ka) and Pit 61/67 (around 11.5 ka). This allowed us to analyze how community structure changed in association with climatic shifts that occurred in North America during the Late Pleistocene and Holocene, and finally compare them with the fauna found in Los Angeles today. We successfully detected the climatic shifts associated with the Last Glacial Maximum together with the Holocene warming. While a sclerophyllous woodland-shrubland is detected for Pit 91 and in modern Los Angeles, a more humid, temperate forest (taiga type) is inferred for Pits 3 and 61/67. We also identified the ecological groups mainly affected by these climatic alterations. The main difference in our communities among different climatic stages is the absence of scansorial predators and several large omnivores in the arid periods (Pit 91 and modern Los Angeles). Finally, since all extinct giant, cursorial hypercarnivores were members of the same functional group, we were also able to detect a structural pattern in the Holocene megafaunal extinction. Founding source: Project CGL2011-25754, MINECO (Spanish Government) and The Research Group BSCH-UCM 910607. FPU predoctoral contract (Spanish Ministry of Education) granted to B.A.G.Y.
The two methodologies tested, ESEM on original teeth and light stereomicroscopy on resin casts, showed similar results on microwear analysis in the glirid Armantomys. Besides, both regions of the tooth crown and dental elements showed the same microwear patterns. The substitution of the species included in the lineage Armantomys aragonensis-A. tricristatus might not imply a change in diet.
Background
Several macroevolutionary hypotheses propose a synchrony between climatic changes and variations in the structure of faunal communities. Some of them focus on the importance of the species ecological specialization because of its effects on evolutionary processes and the resultant patterns. Particularly, Vrba's turnover pulse hypothesis and resource-use hypothesis revolve around the importance of biome inhabitation. In order to test these hypotheses, we used the Biomic Specialization Index, which is based on the number of biomes occupied by each species, and evaluated the changes in the relative importance of generalist and specialist rodents in more than forty fossil sites from the Iberian Plio-Pleistocene.
Results
Our results indicate that there was a decrease in the specialization degree of rodent faunas during the Pliocene due to the global cooling that triggered the onset of the glacial events of the Cenozoic (around 2.75 Ma). The subsequent faunal transition after this critical paleoenvironmental event was characterized by an increase of specialization related to the adaptation to the new environmental conditions, which was mainly associated with the Pleistocene radiation of Arvicolinae (voles).
Conclusions
The pattern of faunal turnover is correlated with the development of the modern glaciations in the Northern Hemisphere around 2.75 Ma, and represents a reorganization of the rodent communities, as suggested by the turnover pulse hypothesis. Our data also support the resource-use hypothesis, which presumes the role of the degree of specialization in resources specifically related to particular biomes as a driver of differential speciation and extinction rates. These results stress the intimate connection between ecological and evolutionary changes."
Debris-flow hosted assemblages dominated by mammalian remains are very scarce in the fossil record and few examples are reported. Herein we present a detailed taphonomic study of Somosaguas-North (Madrid Basin, Spain), a Middle Miocene mammalian-dominated site embedded in debris flow deposits, in order to increase our knowledge of the mode of formation of fossiliferous assemblages in this depositional context. The assemblage includes 6592 large-mammal remains belonging to at least 10 different species. Fossils are found in matrix-supported, poorly-sorted coarse arkosic sandstones and fine conglomerates, which are interpreted as the result of successive debris-flow deposits. Breakage constitutes a pervasive taphonomic alteration in the bone assemblage; however, together with unidentifiable bone fragments, we also found complete to almost complete skeletal elements. Bone remains are isolated, a fact that is indicative of a time of exposure of the carcasses long enough to enable decay and complete disarticulation. There are no associations of elements belonging to the same individual, which suggests that, prior to or during debris-flow transport, bones were profusely dispersed. Based on the taphonomic evidence, we suggest that Somosaguas-North assemblage was formed by successive debris-flow transport and burial of pre-existing thanatocoenoses. Bones from those thanatocoenoses were modified by biostratinomic agents (trampling, weathering) in varying degrees depending on their time of exposure. Debris-flow transport produced further abrasion and breakage in collagen-depleted bones. Our results are congruent with an environmental context of semiarid landscapes presenting long arid periods and highly irregular hydrological seasonality. Finally, we compared the Somosaguas-North assemblage with other debris-flow hosted vertebrate assemblages. Although Somosaguas-North shares taphonomic features with some of these sites, it is not possible to define consistent and single taphonomic patterns for debris-flow assemblages, given the varied taphonomic histories of the remains prior to and during debris-flow transport.
forcing on faunal communities. Using late Miocene rodent faunas (12 to 5 Ma) from two different
biogeographical provinces from southwestern Europe, we asked whether the waxing and waning of faunas
with dissimilar ecological affinities tracked climate in different ways. The latest middle Miocene featured a
fauna dominated by dormice with forest and mixed-habitat affinities. This group declined towards the
Upper Miocene. Rodent taxa with the highest values of richness at the beginning of the Upper Miocene are
generalists in the southern province and specialists of forested habitats in the northern province. Finally, we
identified a third, increasingly significant group of rodents linked to open landscapes towards the end of the
Miocene. These three broad ecological groups showed differential responses to a complex set of
interconnected circumstances, including the biogeographic structure of the study area and climatic changes
throughout time.
The effect of climate change on extant mammal faunas is a frequent topic in ecological research and the analysis of past mammalian communities and their correlated evolution with global climatic change can provide data relevant to this question. Late Pleistocene and Holocene carnivore mammal faunas from the Rancho La Brea Tar Pits (Los Angeles, CA) are highly diverse and well-preserved, and were used to analyze how past climatic shifts shaped the structure of mammalian communities from southwestern North America over the past 30,000 years. Using bibliographical data, we clustered all extant terrestrial carnivores in 11 Carnivore Functional Groups with similar ecological features (diet, locomotion, and body size), and subsequently defined the functional spectra of 26 modern localities from the Nearctic. By means of discriminant analysis, we explored how the ecological structure (functional spectrum) of these communities varies with environmental conditions (type of biome). Morphofunctional analyses of La Brea species allowed us to determine their ecological features and thereby define the functional spectra of communities at different stages (pits). The selected pits varied in age: Pit 91 (around 29 ka), Pit 3 (around 18.5 ka) and Pit 61/67 (around 11.5 ka). This allowed us to analyze how community structure changed in association with climatic shifts that occurred in North America during the Late Pleistocene and Holocene, and finally compare them with the fauna found in Los Angeles today. We successfully detected the climatic shifts associated with the Last Glacial Maximum together with the Holocene warming. While a sclerophyllous woodland-shrubland is detected for Pit 91 and in modern Los Angeles, a more humid, temperate forest (taiga type) is inferred for Pits 3 and 61/67. We also identified the ecological groups mainly affected by these climatic alterations. The main difference in our communities among different climatic stages is the absence of scansorial predators and several large omnivores in the arid periods (Pit 91 and modern Los Angeles). Finally, since all extinct giant, cursorial hypercarnivores were members of the same functional group, we were also able to detect a structural pattern in the Holocene megafaunal extinction. Founding source: Project CGL2011-25754, MINECO (Spanish Government) and The Research Group BSCH-UCM 910607. FPU predoctoral contract (Spanish Ministry of Education) granted to B.A.G.Y.
The two methodologies tested, ESEM on original teeth and light stereomicroscopy on resin casts, showed similar results on microwear analysis in the glirid Armantomys. Besides, both regions of the tooth crown and dental elements showed the same microwear patterns. The substitution of the species included in the lineage Armantomys aragonensis-A. tricristatus might not imply a change in diet.
Background
Several macroevolutionary hypotheses propose a synchrony between climatic changes and variations in the structure of faunal communities. Some of them focus on the importance of the species ecological specialization because of its effects on evolutionary processes and the resultant patterns. Particularly, Vrba's turnover pulse hypothesis and resource-use hypothesis revolve around the importance of biome inhabitation. In order to test these hypotheses, we used the Biomic Specialization Index, which is based on the number of biomes occupied by each species, and evaluated the changes in the relative importance of generalist and specialist rodents in more than forty fossil sites from the Iberian Plio-Pleistocene.
Results
Our results indicate that there was a decrease in the specialization degree of rodent faunas during the Pliocene due to the global cooling that triggered the onset of the glacial events of the Cenozoic (around 2.75 Ma). The subsequent faunal transition after this critical paleoenvironmental event was characterized by an increase of specialization related to the adaptation to the new environmental conditions, which was mainly associated with the Pleistocene radiation of Arvicolinae (voles).
Conclusions
The pattern of faunal turnover is correlated with the development of the modern glaciations in the Northern Hemisphere around 2.75 Ma, and represents a reorganization of the rodent communities, as suggested by the turnover pulse hypothesis. Our data also support the resource-use hypothesis, which presumes the role of the degree of specialization in resources specifically related to particular biomes as a driver of differential speciation and extinction rates. These results stress the intimate connection between ecological and evolutionary changes."