Questions:Spatial levelHow does abundance of small rodents relate with

altitude and latitude?

Climatic levelHow does abundance of small rodents relate with

climate?

Abundance of small mammals along an altitudinal - latitudinal gradient in the Central Andes of Argentina

We explore the data in a graphical way xyplot(ABUND~ALT|lat,groups=lat,type="b",lwd=3)

ABUNDANCE

ALTITUDE

35°LAT

32°LAT

34°LAT

33°LAT

Spatial level

ABUND

lat

a=with(an,tapply(ABUND,list(ALT,lat),mean)) barplot(a,beside=TRUE)

Bar plot of abundance variation per altitude for each latitude.

130

0

230

028

00

330

0

180

0

Abundance peaks at 2300m.

We observed a quadraticrelationship.

Spatial level

We rescaled the latitude and altitude axes: alt=((ALT-1300)/1000) # to standardize the variablelt=(lat-32) We transformed abundance to log, to get a better fit to a normal distribution.ab=log(ABUND)

We performed a linear model: Spatial Model =lm(ab~lt+alt+I(lt^2)+I(alt^2))

Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 2.5076 0.4542 5.521 5.87e-05 ***lt 1.1659 0.5288 2.205 0.04350 * alt 3.3662 0.8422 3.997 0.00117 ** I(lt^2) -0.3981 0.1689 -2.357 0.03246 * I(alt^2) -1.4410 0.4038 -3.568 0.00280 **

Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 0.7555 on 15 degrees of freedomMultiple R-squared: 0.5993, Adjusted R-squared: 0.4924 F-statistic: 5.608 on 4 and 15 DF, p-value: 0.005772

Spatial level

Lollipop3d graph showing the relationship between log-abundance and the spatial predictor variables, altitude and latitude.

Log(abund)=latitude+altitude+latitude2+altitude2

Abundance shows a hump shape pattern along altitude (peak= 2300m) and latitude (peak= 33° S).

Spatial level

Climatic variables: we reduced the variability of all precipitation variables into one PCA (Prec) and all temperature variables into one PCA (Temp).

Temperature seasonality accounts for 94% of the variation in PCA (Temp).

Annual mean precipitation (53%), Precipitation of the wettest season (20%) and Precipitation of the coldest season (20%) accounts for 93% of the variation in PCA (Prec).

PCA

Log abundance has a quadratic relationship with the climatic variables.

Climatic level

We performed a Linear model: Climatic model=lm(log(ABUND)~PCA_Temp+PCA_Prec+I(PCA_Temp^2)+I(PCA_Prec^2))

Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 4.805e+00 2.844e-01 16.895 3.58e-11 ***PCA_Temp -1.027e-04 7.380e-04 -0.139 0.8912 PCA_Prec 1.117e-03 1.278e-03 0.874 0.3958 I(PCA_Temp2) -3.528e-06 1.650e-06 -2.138 0.0494 * I(PCA_Prec2) -1.153e-05 5.416e-06 -2.129 0.0502 .

Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Residual standard error: 0.8337 on 15 degrees of freedomMultiple R-squared: 0.512, Adjusted R-squared: 0.3819 F-statistic: 3.934 on 4 and 15 DF, p-value: 0.02229

Climatic level

Lollipop3d graph showing the relationship between log-abundance and the climatic predictor variables, PCA (Temp), PCA (Prec).

Climatic level

Temperature Seasonality

Abundance is maximum at intermediate values of temperature and precipitation.

Annual mean precipitation Precipitation of the wettest seasonPrecipitation of the coldest season

AIC df dAIC WeightSpatial model 51.8 6 0.0 0.878 Climatic model 55.7 6 3.9 0.122

We compared the spatial and climatic model using the Akaike’s Information Criterion

The spatial fits better than the climatic model.Apparently altitude variability is composed by more than climatic variables.

Final remarks

Conclusion:

How does abundance of small rodents relate with altitude and latitude?In a quadratic relationship, with a peak at intermediate altitudes and latitudes.

How does abundance of small rodents relate with climate? In a quadratic relationship peaking at intermediate Temperature Seasonality and

Precipitation.

Thank you