Changes of community structure in response to competition usually take place on timescales that a... more Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10–100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and heterogeneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the longterm effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end-Permian mass extinction. We suggest that these non-actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.
A new sampling of Early Triassic (Griesbachian) conodonts is obtained from the microbialite overl... more A new sampling of Early Triassic (Griesbachian) conodonts is obtained from the microbialite overlying the latest Permian peri-reefal shallow water limestone in Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). High resolution sam-pling in the lower twelve meters of the Luolou Formation provides rather diversified conodont faunas and allows const-ructing a well resolved conodont distribution for this crucial earliest Triassic interval. In the Wuzhuan section, the nine meters thick microbialite is bracketed by two calcarenite beds and contains several fossiliferous lenses. The co-occurrence of typical Permian foraminifera such as Paraglobivalvulina mira (Reitlinger) and Dagmarita chanakchiensis (Reitlinger) in the calcarenite underlying the microbialite indicates a late Permian age. Our preliminary results indicate the presence of one residual maximal horizon (RMH) based on conodont faunas in the microbialite and of a second one in the overlying calca-renite. The lowest RMH o...
We describe a new Early Triassic (Griesbachian)
succession of conodont faunas from a high-resolut... more We describe a new Early Triassic (Griesbachian) succession of conodont faunas from a high-resolution sampling of the basal Early Triassic microbial limestone and the base of the overlying unit at the Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). The microbial limestone records the earliest phase of the Early Triassic biotic recovery after the end-Permian mass extinction. For the first time, rich conodont faunas are reported from within the microbialite. The faunas from Wuzhuan are largely dominated by anchignathodontids, including several Isarcicella species, which were previously documented only from strata above the microbialite. A total of 14 conodont species assigned to three genera is recorded from the Wuzhuan section. Starting from the base of the microbialite upwards, several species are sequentially added to the conodont assemblage. The alpha diversity peaks at the top of the microbialite. The conodont record in the considered microbialite interval at Wuzhuan is presumably unaffected by local ecological changes. It therefore more likely represents an evolutionary rather than an ecological pattern. We compare the Wuzhuan’s conodont record with a well-supported phylogenetic model and suggest that the sequence of first occurrences at Wuzhuan is the closest to the ‘true’ sequence of evolutionary events that took place during this Griesbachian radiation of anchignathodontids. Based on comparisons with the GSSP section at Meishan, we suggest further that the first occurrence of Hindeodus parvus in Meishan does not correspond to its first appearance datum.
Changes of community structure in response to competition usually take place on timescales that a... more Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10–100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and heterogeneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the longterm effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end-Permian mass extinction. We suggest that these non-actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.
A new sampling of Early Triassic (Griesbachian) conodonts is obtained from the microbialite overl... more A new sampling of Early Triassic (Griesbachian) conodonts is obtained from the microbialite overlying the latest Permian peri-reefal shallow water limestone in Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). High resolution sam-pling in the lower twelve meters of the Luolou Formation provides rather diversified conodont faunas and allows const-ructing a well resolved conodont distribution for this crucial earliest Triassic interval. In the Wuzhuan section, the nine meters thick microbialite is bracketed by two calcarenite beds and contains several fossiliferous lenses. The co-occurrence of typical Permian foraminifera such as Paraglobivalvulina mira (Reitlinger) and Dagmarita chanakchiensis (Reitlinger) in the calcarenite underlying the microbialite indicates a late Permian age. Our preliminary results indicate the presence of one residual maximal horizon (RMH) based on conodont faunas in the microbialite and of a second one in the overlying calca-renite. The lowest RMH o...
We describe a new Early Triassic (Griesbachian)
succession of conodont faunas from a high-resolut... more We describe a new Early Triassic (Griesbachian) succession of conodont faunas from a high-resolution sampling of the basal Early Triassic microbial limestone and the base of the overlying unit at the Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). The microbial limestone records the earliest phase of the Early Triassic biotic recovery after the end-Permian mass extinction. For the first time, rich conodont faunas are reported from within the microbialite. The faunas from Wuzhuan are largely dominated by anchignathodontids, including several Isarcicella species, which were previously documented only from strata above the microbialite. A total of 14 conodont species assigned to three genera is recorded from the Wuzhuan section. Starting from the base of the microbialite upwards, several species are sequentially added to the conodont assemblage. The alpha diversity peaks at the top of the microbialite. The conodont record in the considered microbialite interval at Wuzhuan is presumably unaffected by local ecological changes. It therefore more likely represents an evolutionary rather than an ecological pattern. We compare the Wuzhuan’s conodont record with a well-supported phylogenetic model and suggest that the sequence of first occurrences at Wuzhuan is the closest to the ‘true’ sequence of evolutionary events that took place during this Griesbachian radiation of anchignathodontids. Based on comparisons with the GSSP section at Meishan, we suggest further that the first occurrence of Hindeodus parvus in Meishan does not correspond to its first appearance datum.
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Papers by Morgane Brosse
benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification
model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.
succession of conodont faunas from a high-resolution sampling
of the basal Early Triassic microbial limestone and the
base of the overlying unit at the Wuzhuan section (Nanpanjiang
Basin, Guangxi, South China). The microbial limestone
records the earliest phase of the Early Triassic biotic
recovery after the end-Permian mass extinction. For the first
time, rich conodont faunas are reported from within the microbialite.
The faunas from Wuzhuan are largely dominated
by anchignathodontids, including several Isarcicella species,
which were previously documented only from strata above
the microbialite. A total of 14 conodont species assigned to
three genera is recorded from the Wuzhuan section. Starting
from the base of the microbialite upwards, several species
are sequentially added to the conodont assemblage. The
alpha diversity peaks at the top of the microbialite. The
conodont record in the considered microbialite interval at
Wuzhuan is presumably unaffected by local ecological
changes. It therefore more likely represents an evolutionary
rather than an ecological pattern. We compare the Wuzhuan’s
conodont record with a well-supported phylogenetic
model and suggest that the sequence of first occurrences at
Wuzhuan is the closest to the ‘true’ sequence of evolutionary
events that took place during this Griesbachian radiation of
anchignathodontids. Based on comparisons with the GSSP
section at Meishan, we suggest further that the first occurrence
of Hindeodus parvus in Meishan does not correspond
to its first appearance datum.
benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification
model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.
succession of conodont faunas from a high-resolution sampling
of the basal Early Triassic microbial limestone and the
base of the overlying unit at the Wuzhuan section (Nanpanjiang
Basin, Guangxi, South China). The microbial limestone
records the earliest phase of the Early Triassic biotic
recovery after the end-Permian mass extinction. For the first
time, rich conodont faunas are reported from within the microbialite.
The faunas from Wuzhuan are largely dominated
by anchignathodontids, including several Isarcicella species,
which were previously documented only from strata above
the microbialite. A total of 14 conodont species assigned to
three genera is recorded from the Wuzhuan section. Starting
from the base of the microbialite upwards, several species
are sequentially added to the conodont assemblage. The
alpha diversity peaks at the top of the microbialite. The
conodont record in the considered microbialite interval at
Wuzhuan is presumably unaffected by local ecological
changes. It therefore more likely represents an evolutionary
rather than an ecological pattern. We compare the Wuzhuan’s
conodont record with a well-supported phylogenetic
model and suggest that the sequence of first occurrences at
Wuzhuan is the closest to the ‘true’ sequence of evolutionary
events that took place during this Griesbachian radiation of
anchignathodontids. Based on comparisons with the GSSP
section at Meishan, we suggest further that the first occurrence
of Hindeodus parvus in Meishan does not correspond
to its first appearance datum.