Climate, isolation and intraspecific competition affect morphological traits in an endangered steppe bird, the Dupont’s Lark Chersophilus duponti

Figures & data

Figure 1. Geographic origins of Dupont’s Lark samples in Spain, Morocco and Tunisia during the period 1986–2013. Black dots indicate capture sites, black crosses mark Spanish and Moroccan population centroids based on geographic coordinates of capture points. For a global distribution map of the species, see de Juana and Suárez (2016). For a more detailed distribution in Spain see Suárez (2010) and, in Morocco, García et al. (2008b).

Table 1. Response variables for Dupont’s Lark morphological analysis and their ecological meaning.

Response variable	Direct/indirect^a	Ecological meaning
Body size	Indirect	Thermoregulation capacity
Wing morphology^b	Indirect	Flight capacity
Bill length	Direct	Thermoregulation and song capacity
Bill volume	Indirect	Thermoregulation and song capacity
Tarsus length	Direct	Thermoregulation and locomotion capacity

^aDirect measures are used as obtained in the field, indirect ones are estimations from direct data through a PCA or a mathematical formula (see Methods, biometry).

^bThree different variables analysed as estimators of wing morphology, resulting from the 3 principal components with eigenvalues greater than 1 (see online Appendix A2).

Table 2. Predictors used in model construction to assess Dupont’s Lark biometry, and their ecological meaning. An X indicates that the predictor was included in the model for each response variable.

Explanatory variable	Ecological meaning	Body size	Wing morf.^a	Bill length^a	Bill volume^a	Tarsus length^b
Climate
Temperature range	Degree of climate seasonality	X
Minimum temperature	Lower extreme of thermal stress	X
Maximum temperature	Upper extreme of thermal stress			X	X	X
April temperature	Temp. on breeding season	X
Annual rainfall	Water availability	X
Isolation
Distance to centroid	Isolation from central populations	X	X	X	X	X
Distance/Pop.Size	Isolation corrected for Pop. Size	X	X	X	X	X
Intraspecific competition
Population density	Competition (pure effect)	X	X	X	X	X
Population size	Competition (pure effect)	X	X	X	X	X
Pop.Dens.*Pop.Size	Interaction of both effects	X	X	X	X	X

^aBody size included as covariable.

^bWing length included as covariable.

Table 3. Sexual dimorphism in Dupont’s Lark, mean and standard deviation of each morphological trait. P-value by means of anova type III SS after a GLMM.

	n	Male	Female	P
Body size	600	89.18 ± 1.79	82.36 ± 2.29	<0.001
Wing morphology PC1^a	350	−38.89 ± 2.59	−34.23 ± 2.36	<0.001
Wing morphology PC2^a	350	−5.59 ± 1.21	−5.30 ± 0.71	0.015
Wing morphology PC3^a	350	−14.81 ± 1.52	−13.71 ± 1.63	0.042
Bill length^a	484	23.81 ± 1.00	21.63 ± 1.22	<0.001
Bill volume^a	445	592.92 ± 67.32	492.26 ± 85.73	0.174
Tarsus length^b	600	24.01 ± 0.84	23.07 ± 0.76	0.185

Notes: The sample size is the largest for each morphological variable, as not all experimental units accounted for the complete set of measurements.

^aControlled for body size using b. s. index.

^bControlled for body size using wing length.

Table 4. Morphological differences in male Dupont’s Larks among the three unconnected regions: Spain, Morocco and Tunisia. Mean and standard deviation of each morphological trait. P-value by means of anova type III SS conducted after a GLMM. Post hoc Dunnett’s modified Tukey–Kramer pairwise multiple comparison test was carried out to assess significant differences, indicated with superscript letters, meaning that regions sharing the same letter do not differ in that morphological trait. In the case of Wing morph. PC1, we obtained a significant value in the anova test but no significance in the post hoc comparison, as the latter is more conservative (Cardinal & Aitken 2006).

	n	Spain	Morocco	Tunisia	P
Body size	673	89.18 ± 1.79^a	91.25 ± 1.98^b	91.87 ± 1.58^c	<0.001
Wing morph. PC1^1	451	−38.07 ± 2.55^a	−38.58 ± 4.42^a	−40.57 ± 4.50^a	0.006
Wing morph. PC2^1	451	−6.67 ± 1.22^a	−8.40 ± 6.70^b	−6.39 ± 1.46^ab	<0.001
Wing morph. PC3^1	451	−15.87 ± 1.57	−16.04 ± 2.85	−15.75 ± 3.27	0.278
Bill length^1	574	23.81 ± 1.00^a	24.71 ± 1.39^b	26.22 ± 1.66^c	<0.001
Bill volume^1	542	592.92 ± 67.32^a	624,46 ± 68.75^b	739.34 ± 87.23^c	<0.001
Tarsus length^2	673	24.01 ± 0.84	24.16 ± 1.01	24.60 ± 0.81	0.221

Notes: The sample size is the largest for each morphological variable, as not all experimental units accounted for the complete set of measurements.

¹Controlled for body size using b. s. index.

²Controlled for body size using wing length.

Table 5. Model averaging results for each morphological response variable in male Dupont’s Larks: variables included in the averaged model, weighted estimator, unconditional standard error following Burnham and Anderson’s revised formula (2004), relative importance, z and P values.

		Spain					Morocco
Averaged model	Parameter	Estimate	USE	Rel. imp	z	P	Estimate	USE	Rel. imp	z	P
Body size	(Intercept)	−0.106	0.212	1.00	0.499	0.617	0.003	0.141	1.00	0.026	0.979
	Temperature range	0.022	0.043	0.04	0.533	0.593	0.366	0.189	0.48	1.933	0.053
	Minimum temperature	0.051	0.075	0.08	0.680	0.496	0.128	0.280	0.23	0.459	0.646
	April temperature	0.062	0.080	0.08	0.774	0.438	−1.324	0.550	0.92	2.405	0.016*
	Annual rainfall	0.004	0.095	0.07	0.051	0.959	−1.544	0.586	0.97	2.631	0.008*
	Distance/Pop.Size	0.029	0.050	0.05	0.575	0.565	−0.256	0.621	0.24	0.412	0.680
	Distance to centroid	−0.022	0.067	0.07	0.326	0.744	0.226	0.582	0.23	0.388	0.697
	Population size	−0.126	0.047	0.70	2.662	0.007*	−0.215	0.153	0.41	1.398	0.162
	Population density	−0.019	0.182	0.09	0.106	0.915	−0.442	0.242	0.55	1.823	0.068
	Pop.Dens.*Pop.Size	−0.160	0.296	0.01	0.540	0.589	−0.695	0.274	0.31	2.532	0.011*
Wing PC1	(Intercept)	0.001	0.144	1.00	0.007	0.994	−0.090	0.352	1.00	0.257	0.797
	Body size^a	0.127	0.054	0.43	2.338	0.0194*	0.041	0.106	0.09	0.388	0.698
	Distance/Pop.Size	0.001	0.072	0.06	0.022	0.982	3.073	4.160	0.22	0.739	0.460
	Distance to centroid	0.026	0.083	0.08	0.323	0.746	−0.823	0.947	0.26	0.870	0.384
	Population size	−0.207	0.096	0.89	2.145	0.031*	0.240	0.507	0.23	0.474	0.635
	Population density	−0.694	0.680	0.16	1.020	0.307	0.478	0.882	0.23	0.542	0.588
	Pop.Dens.*Pop.Size	−0.655	0.318	0.10	2.057	0.039*	−6.737	4.116	0.10	1.637	0.102
Wing PC2	(Intercept)	−1.001	1.498	1.00	0.668	0.504	0.019	0.212	1.00	0.091	0.927
	Body size^a	0.063	0.048	0.10	1.307	0.191	0.168	0.106	0.24	1.574	0.115
	Distance/Pop.Size	−0.093	0.066	0.18	1.395	0.163	0.551	1.870	0.25	0.295	0.768
	Distance to centroid	−0.134	0.053	0.54	2.513	0.012*	0.222	0.582	0.25	0.382	0.702
	Population size	0.063	0.079	0.11	0.807	0.420	−0.233	0.174	0.63	1.341	0.180
	Population density	0.106	0.109	0.29	0.970	0.332	0.413	0.592	0.26	0.698	0.485
	Pop.Dens.*Pop.Size	−0.042	0.304	0.01	0.140	0.889	−1.545	3.203	0.10	0.483	0.629
Wing PC3	(Intercept)	0.297	0.497	1.00	0.599	0.549	0.048	0.248	1.00	0.194	0.846
	Body size^a	0.007	0.053	0.05	0.139	0.889	−0.148	0.106	0.21	1.403	0.161
	Distance/Pop.Size	−0.120	0.083	0.16	1.441	0.149	−0.209	1.440	0.28	0.146	0.884
	Distance to centroid	0.023	0.078	0.07	0.305	0.760	−0.141	0.509	0.27	0.277	0.782
	Population size	−0.269	0.187	0.27	1.434	0.151	0.175	0.180	0.38	0.976	0.329
	Population density	−0.419	0.784	0.48	0.534	0.593	−0.329	0.397	0.39	0.828	0.408
	Pop.Dens.*Pop.Size	−0.878	0.343	0.18	2.558	0.010*	0.197	2.953	0.08	0.067	0.947
Bill length	(Intercept)	−0.557	0.359	1.00	1.549	0.121	0.042	0.302	1.00	0.142	0.886
	Body size^a	0.215	0.043	1.00	5.001	<0.001*	0.360	0.080	1.00	4.459	<0.001*
	Maximum temperature	−0.030	0.047	0.05	0.652	0.514	0.252	0.084	0.86	2.982	0.002*
	Distance/Pop.Size	−0.062	0.044	0.10	1.412	0.158	−0.049	0.230	0.12	0.214	0.830
	Distance to centroid	−0.030	0.056	0.06	0.543	0.587	−0.119	0.174	0.14	0.684	0.493
	Population size	−0.022	0.117	0.06	0.189	0.850	−0.004	0.089	0.08	0.050	0.960
	Population density	−0.167	0.284	0.11	0.590	0.555	0.023	0.123	0.10	0.192	0.847
	Pop.Dens.*Pop.Size	−0.062	0.285	0.01	2.325	0.020*	0.560	0.380	0.01	1.473	0.140
Bill volume	(Intercept)	−0.333	0.277	1.00	1.203	0.228	0.007	0.091	1.00	0.080	0.936
	Body size^a	0.170	0.046	0.97	3.632	<0.001*	0.206	0.091	0.52	2.254	0.024*
	Maximum temperature	0.271	0.052	1.00	5.159	<0.001*	0.081	0.099	0.11	0.810	0.417
	Distance/Pop.Size	0.019	0.052	0.05	0.360	0.718	−0.093	0.507	0.17	0.185	0.853
	Distance to centroid	−0.027	0.062	0.06	0.446	0.655	−0.045	0.423	0.15	0.109	0.913
	Population size	−0.153	0.143	0.11	1.066	0.286	0.276	0.104	0.85	2.654	0.007*
	Population density	−0.322	0.341	0.29	0.945	0.344	0.053	0.157	0.16	0.340	0.733
	Pop.Dens.*Pop.Size	−0.631	0.261	0.06	2.410	0.015*	0.492	0.397	0.06	1.241	0.214
Tarsus length	(Intercept)	−0.212	0.155	1.00	0.155	0.170	−0.003	0.095	1.00	0.036	0.972
	Wing length^a	0.210	0.043	1.00	4.835	<0.001*	0.080	0.094	0.11	0.835	0.404
	Maximum temperature	−0.006	0.049	0.04	0.125	0.901	−0.012	0.101	0.09	0.126	0.899
	Distance/Pop.Size	0.048	0.064	0.06	0.750	0.453	−0.302	0.359	0.40	0.841	0.400
	Distance to centroid	−0.096	0.059	0.17	1.604	0.109	−0.193	0.421	0.39	0.459	0.646
	Population size	−0.018	0.058	0.05	0.315	0.753	−0.210	0.155	0.27	1.357	0.175
	Population density	−0.138	0.067	0.36	2.054	0.040*	−0.251	0.210	0.31	1.196	0.232
	Pop.Dens.*Pop.Size	0.040	0.258	<0.01	0.157	0.875	−0.314	0.339	0.05	0.925	0.355

^aIntroduced as covariable.

De Juana, E. & Suárez, F. 2016. Dupont's Lark (Chersophilus Duponti). In Del Hoyo, J., Elliott, A., Sargatal, J., Christie, D. A. & De Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. http://www.hbw.com/node/57638.

 Google Scholar

Suárez, F. 2010. La Alondra Ricotí (Chersophilus duponti). Dirección General Para La Biodiversidad. Ministerio de Medio Ambiente y Medio Rural y Marino, Madrid.

 Google Scholar

García, J.T., Suárez, F., Garza, V., Justribó, J.H., Oñate, J., Hervás, I., Calero, M. & García De La Morena, E.L. 2008b. Assessing the distribution, habitat, and population size of the threatened Dupont's Lark Chersophilus duponti in Morocco: lessons for conservation. Oryx 42: 592-599. doi: 10.1017/S0030605308000653

 Web of Science ®Google Scholar

Cardinal, R.N. & Aitken, M.R.F. 2006. ANOVA for the Behavioural Sciences Researcher. Lawrence Erlbaum Associates, New York.

 Google Scholar

Burnham, K. & Anderson, D. 2004. Multimodel inference: understanding AIC and BIC in model selection. Sociolog. Methods Res. 33: 261–304. doi: 10.1177/0049124104268644

 Web of Science ®Google Scholar