TEMPORAL SHIFTS AND NICHE OVERLAPPING IN Copestylum COMMUNITY STRUCTURE IN A SCRUBLAND WITH CATTLE G

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TEMPORAL SHIFTS AND NICHE OVERLAPPING IN
Copestylum COMMUNITY STRUCTURE IN A SCRUBLAND
WITH CATTLE GRAZING MANAGEMENT IN MÉXICO

• 1Ana Paola Martínez-Falcón, 1Ma. Ángeles
  Marcos-García and
• 2Claudia E. Moreno
• 1Centro Iberoamericano de la Biodiversidad,
  Universidad de Alicante, Spain 2Centro de
  Investigaciones Biológicas, Universidad Autónoma
  del Estado de Hidalgo, Mexico.

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INTRODUCTION

• Temporal community dynamics can be evaluated by
  assessing the continual presence of the component
  species and whether their abundances are constant
  (Magurran and Philip, 2007).

• All communities are dynamic and this is related
  to environmental variability, land-use changes
  and intensity of interspecific interactions
  (Shuri, 2007).

• In the context of niche overlap, competitive
  interactions are an important mechanism
  structuring natural communities. Nowadays one
  important question in community ecology is How
  do coexisting species partition spatial and
  temporal resources?

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INTRODUCTION

• Copestylum (Diptera Syrphidae) is an endemic New
  World syrphid lineage and it is one of the most
  speciose Neotropical syrphid genera. Larvae of
  Copestylum are saprofagous and they most
  frequently reported breeding medium is decaying
  cacti.
• There is little knowledge about the life history
  and ecology of the syrphids living in decaying
  cacti.

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OBJECTIVES

• In this study we address the following questions
  
• 1) How has Copestylum species diversity changed
  over time and type of management?
• 2) What is the relative contribution of a and ß
  -diversity on total diversity?
• 3) How much niche overlap have in dry and rainy
  Copestylum communities on decaying cacti?

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METHODS Study Area

• This study was carried out in a Biosphere Reserve
  Barranca de Metztitlán Hidalgo, Mexico.
• Two different sites were sampled
• MCN (Undisturbed semiarid scrub with columnar
  cacti)
• MCP (Disturbed semiarid cactus scrub)
• Disturbed site by cattle activities.
• Both at 1600 m altitude.
• Dry-hot semiarid scrubs with a mean annual
  temperature over 18C (64F).

MCN
MCP
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Field Sampling Methods

• We carried out six sampling events (three on dry
  season and three on rainy season) in 2007.
• Sampling effort 8 parcels (25 x 4 m) on each
  area.

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METHODS Fieldwork and Rearing in the Laboratory
Larvae were located by hand searching and were
reared in plastic containers in temperature
controlled chambers. Puparia were reared
separately and adults emerged were identified
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METHODS Data analysis

• We used EstimateS v.7.5.0 (Colwell, 2005) to
  generate species accumulation curves for our four
  communities (between two habitat conditions
  undisturbed and no disturbed and two seasons dry
  and rainy).
• We compared the community structure, as well of
  alpha, beta, and gamma diversity in crasicaule
  scrublands between the four communities. The beta
  analyses were computed using PRIMER (Clarke y
  Gorley, 2001).
• The additive partitioning of total diversity was
  performed using PARTITION (Crist. et al., 2003).
• We use Czechanowski index to analyze niche
  overlap. We used a null model analysis (R3) to
  quantify niche overlap among all species
  according with the season. All simulations were
  carried out with EcoSim software (Gotelli and
  Entsminger, 1999).

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RESULTS Completeness of the inventory
We recorded the presence of 12 species during the
year-long study with 3329 specimens. We breed
hoverflies from five species of cacti
(Cilindropuntia tunicata, Echinocereus
cinerascens, Myrtillocactus geometrizans, Opuntia
ficus-indica and Isolatocereus dumortieri). Our
inventories were more than 90 complete according
with Chao 1 estimators. I. dumortieri was the
cactaceae with the highest number of specimens
and richness of Copestylum.
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RESULTS Species Richness
Comparing the species accumulation curves (Mau
tau function) suggest that there were no
statistical differences in species richness among
communities because the overlap of confidence
intervals (CI 95).
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RESULTS Diversity

• All communities have differences in diversity
  (Plt0.05). Analysis of community structure
  indicates a significant decrease (Plt0.05) in
  diversity in disturbed community on dry season
  (H1.14) and high diversity in undisturbed
  community on rainy season (H1.93).

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RESULTS Rank abundance

• Species codes A C. simile, B C. limbipenne, C
  C. latum, D C. marginatum, E C. posticum, F C.
  mila, G C. hidalgense, H C. sica, I C.
  mexicanum, J C. tetetzoi, K C. violaceum, L C.
  truncatum.
• We found differences in the ranking position of
  the species between sites. All communities had a
  dominant structure
• C. marginatum was the most abundant in the
  disturbed site.
• C. hidalgense, C. tetetzoi and C. mexicanum were
  exclusive of some communities.

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RESULTS Beta diversity

• According to the Bray-Curtis index, species
  composition turnover was greater between seasons
  than among management types. These results
  suggest important effects of seasonality more
  than management for Copestylum species
  communities.

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RESULTS gamma diversity
ßseasons
a
a
aparcels ßparcels

• The beta temporal was essential to keep alfa and
  gamma diversity whereas the impact of grazing
  have less importance in gamma diversity while
  Shannon diversity was largely determined at scale
  of individual units (spatial effects).

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RESULTS Niche overlapping

• The pairwise Czechanowski index show in general
  high niche overlap in dry season and medium on
  rainy season
• Species ocurrences were dynamic, with
  considerably turnover in composition.

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RESULTS Niche overlapping
Dry
Rainy

• Regarding the existence of a guild structure,
  cluster analysis show two main groups for dry
  season data and three for rainy season.
• On a seasonal scale niche overlap and pairwise
  associations were aggregated on dry season and
  more segregated on rainy season.
• C. mila and C. latum have the highest pairwise
  value for both seasons.

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DISCUSION
Scrubland management
Temporal changes explain diversity patterns
Competition Resource partition Decomposition
processes
Coexistence
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CONCLUSION
Our results suggest that in crasicaule
scrublands Copestylum communities are more
important the temporal changes than anthropogenic
disturbance in diversity patterns. Otherwise, the
niche overlapping results suggest Copestylum
species partition recourses at temporal scales.
Further research is needed to understand the
competition-colonization trade offs of Copestylum
assemblages on decaying cacti.
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Acknowledgements
This research was supported by AECID (grant
A/020305/08), FOMIX CONACYTHidalgo (grant 95828)
and CONACYT (grant 84127). APM acknowledge the
scholarship provided by The Alßan programme, the
European Union Programme of High Level
Scholarships for Latin America, scholarship No.
E07D401138MX.