Getting closer: study at mesogeographical scale of cryptic speciation in Hormogaster elisae (Oligochaeta, Hormogastridae) D. Fernández-Marchán1*, R. Fernández2, M. Novo3, DJ Díaz Cosín1 1 Departamento de Zoología y Antropología Física, Facultad de Biología, Universidad Complutense de Madrid, C/ José Antonio Nováis, 28040, Madrid, Spain 2 Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA. 3 Cardiff School of Biosciences, Cardiff University, BIOSI 1, Museum Avenue, Cardiff CF10 3AT, UK. *Author for correspondence:
[email protected] *
Introduction Several studies have shown earthworms as ideal subjects for cryptic speciation research. Novo et al (2010) described the presence of at least five cryptic species in Hormogaster elisae (Oligochaeta, Hormogastridae) in Central Iberian Peninsula. Following their results, these species never appear together.
* * *
*
Lozoya *
*
Soto del Real *
*
Materials and methods In the present study, the limits of three of those cryptic species were explored by sampling along three transects (10-13 km long) between the closest previously-detected localities of the cryptic species I, II and V. Our aim was to elucidate whether those cryptic species are geographically isolated as previously suggested and if their ranges superimpose.
* *
*
*
*
*
* * * *
* *
C la d e 2
Monte Holiday
Miraflores + Guadalix
*
*
Fourteen new populations were studied and placed in the context of the phylogeny of the previously-known cryptic species based on the sequences of the mitochondrial genes cytochrome C oxidase subunit I (COI), a fragment including 16S rRNA and tRNAs and the nuclear genes 28S rRNA, and histone 3 (H3). Genetic variability, genetic divergence and genetic flow were estimated. The spatial distribution of genetic divergence was represented using R and ArcGIS 9.3 following Dinca et al (2013). Main soil variables (soil texture components, content of organic matter and nitrogen, and pH) were analyzed from a soil sample for each locality and compared statistically between the different populations in order to test for existence of ecological preferences.
* *
*
*
*
C la d e 4 ( sp I V & V ) C la d e 3
El Pardo
*
*
Navas de Buitrago El Verdugal Lozoyuela E l C uad ró n E l C hap arral *
C la d e 1
P R1 + P R2 + P R3
Venturada Redueña * P R4 * Cantoblanco * *
P isc is+ P N T 2 + P N T 3
* 0,07
Bayesian inference of the phylogenetic tree based on the concatenated sequence of COI, 16S, 28S and H3. Posterior probability/bootstrap support values (of a Maximum Likelihood analysis) higher than 0.9/70 are shown as asteriscs.
Low genetic divergence
Lozoyuela Lozoya
Monte Holiday
El Verdugal
El Cuadrón 0 0,5 1
2
3
4 Kilometers
Navas de Buitrago
MGD between clades*: 16% MGD within clades*: 1.2/3.8% Border: 2960 meters *excluding Lozoya (MGD: Mean genetic divergence) El Chaparral
Redueña
Piscis Miraflores Venturada
PNT2-3
Soto del Real
Guadalix 0 0,5 1
2
3
4 Kilometers
MGD between clades: 14.5% MGD within clades: 1/4% Border: 700 meters Cantoblanco El Pardo
PR4
PR1 PR2
PR3 0 0,5 1
High genetic divergence
4 Kilometers
Results High genetic divergences (from 13.3% to 17.7% for COI) were found between the populations assigned to each clade. This, together with the absence of gene flow (FST values over 0.9) demonstrate the existence of a clear border between their ranges located between 0.7 and 3 kilometers in each case.
% Fine sand
% Coarse sand
F(2,32)=6.9474 p=0.00312
2 Clade
4
Statistically significant differences in four soil texture variables (percentages of coarse sand, fine sand, fine silt and clay) between the clades I, II and IV were found. Thus, the existence of some kind of ecological preferences in the different cryptic species can’t be ruled out.
1
2 Clade
4
% Clay
% Fine silt
2 Clade
4
1
2 Clade
Conclusions These results open several questions about the systematic implications, speciation model (allopatric or parapatric) and the role of competition or habitat selection in this process. Bibliography Novo M, Almodóvar A, Fernández R, Trigo D, Díaz Cosín DJ (2010) Cryptic speciation of hormogastrid earthworms revealed by mitochondrial and nuclear data. Molecular Phylogenetics and Evolution. 56: 507512 Dinca V, Wiklund C, Lukhtanov VA, Kodandaramaiah U, Norén K, Dapporto L, Wahlberg N, Vila R, Friberg M (2013) Reproductive isolation and patterns of genetic differentiation in a cryptic butterfly species complex. Journal of Evolutionary Biology, 26(10), 2095-2106.
F(2,32)=3.5635 p=0.04007
F(2,32)=2.5504 p=0.09381
1
3
MGD between clades: 17% MGD within clades: 0.3/4.7% Border: 2810 meters
F(2,32)=3.1315 p=0.05727
1
2
4
