Research Article |
Corresponding author: Fabio Leonardo Meza-Joya ( fleonardo78@gmail.com ) Academic editor: Maria-Marta Cigliano
© 2022 Fabio Leonardo Meza-Joya, Mary Morgan-Richards, Steven A. Trewick.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Meza-Joya FL, Morgan-Richards M, Trewick SA (2022) Relationships among body size components of three flightless New Zealand grasshopper species (Orthoptera, Acrididae) and their ecological applications. Journal of Orthoptera Research 31(1): 91-103. https://doi.org/10.3897/jor.31.79819
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Body size is perhaps the most fundamental property of an organism and is central to ecology at multiple scales, yet obtaining accurate estimates of ecologically meaningful size metrics, such as body mass, is often impractical. Allometric scaling and mass-to-mass relationships have been used as alternative approaches to model the expected body mass of many species. However, models for predicting body size in key herbivorous insects, such as grasshoppers, exist only at the family level. To address this data gap, we collected empirical body size data (hind femur length and width, pronotum length, live fresh mass, ethanol-preserved mass, and dry mass) from 368 adult grasshoppers of three flightless species at Hamilton Peak, Southern Alps, New Zealand. We examined the relationships among body size components across all species using linear and non-linear regression models. Femur length and preserved mass were robust predictors of both fresh mass and dry mass across all species; however, regressions using preserved mass as a predictor always showed higher predictive power than those using femur length. Based on our results, we developed species-specific statistical linear mixed-effects models to estimate the fresh and dry masses of individual grasshoppers from their preserved mass and femur length. Including sex as an additional co-variate increased model fit in some cases but did not produce better estimates than traditional mass-to-mass and allometric scaling regressions. Overall, our results showed that two easy-to-measure, unambiguous, highly repeatable, and non-destructive size measures (i.e., preserved mass and femur length) can predict, to an informative level of accuracy, fresh and dry body mass across three flightless grasshopper species. Knowledge about the relationships between body dimensions and body mass estimates in these grasshoppers has several important ecological applications, which are discussed.
allometric scaling, body mass, linear body dimension, mass-to-mass relationships, predictive models
Organism body size is one of the most important axes in ecology, as it is related to nearly all biological processes, from individual performance to ecosystem function (
Adult body size in Orthoptera is generally expressed in terms of length and mass, each of which is controlled by both genetic and environmental factors that operate through molecular and physiological mechanisms (
Body mass is the most meaningful size metric, as it is directly linked with metabolic rate and is affected by environmental conditions (
Allometric scaling rules applied to co-varying traits can be used to predict an organism’s body mass based on an easy-to-obtain body length measurement, thus avoiding the use of problematic body mass estimators (
Short-horn grasshoppers (Orthoptera: Acrididae) are among the most diverse (> 6,700 described species) and ubiquitous fauna of grassland ecosystems around the world (
Body size data have been accumulated for New Zealand grasshoppers mostly as linear dimensions: hind femur length and width, and pronotum length (e.g.,
Adult endemic, brachypterous, and flightless grasshopper species from Hamilton Peak in the Southern Alps, New Zealand. A. Brachaspis nivalis female; B. Paprides nitidus female; C. Sigaus australis male; D. Body dimensions used as proxies of overall body size in this study: morphometric data were collected for hind femur length (FL), hind femur width (FW), and pronotum length (PL).
Specimen collection and measurements.—A total of 368 complete adult specimens (no missing appendages) representing three grasshopper species (B. nivalis 61♂, 71♀; P. nitidus 73♂, 73♀; S. australis 42♂, 48♀) were collected on Hamilton Peak in the Craigieburn Range, New Zealand (-43.129, 171.688; WGS84). Sampling was done by hand, capturing grasshoppers disturbed by walking at five sites at ~100 m elevation intervals (BR1 to BR5) from 1,383 to 1,817 m asl, to capture as much local variation in body size as possible. Species and sex were recorded from live specimens in the field and were later corroborated upon processing based on morphological features (e.g., body color pattern, pronotum shape, and body shape and size) following
Grasshoppers were weighed alive after cooling to 4°C, then frozen overnight before being preserved in 95% ethanol for DNA preservation. Specimens were weighed using a Sartorius Quintix35–1S digital scale (Sartorius Lab Instruments GmbH & Co, Goettingen, Germany) accurate to 0.001 g. We measured the left hind femur length (hereafter femur length) and width (hereafter femur width), and pronotum length of specimens (Fig.
To quantify the effects of our preservation method on body mass estimates, we remeasured the body mass of all specimens after two and four months of storage in ethanol. Once all other measurements were completed, a random subsample of 50 specimens of each species (25 males and 25 females) were dried in an oven at 60°C for at least 96 h, until their mass ceased to change, and were then weighed. To assess measurement repeatability, we randomly selected five males and five females of each species and remeasured and reweighed them three times in random order.
Data analysis and model structures.—Repeatability (R) was calculated independently for species and sexes with the R package rptR (
A. Density distributions of body mass in three flightless New Zealand grasshopper species when alive (turquoise) and after ethanol-preservation for two (dark yellow) and four months (black); B. The distribution of the difference in mass between live and 4-month preserved specimens pooled for all three species and partitioned by sex. Mean values for male (-0.012 g) and females (-0.029 g) are indicate by dashed lines. Marginal rug indicates individual observations of body mass.
We explored mass-to-mass ratios between ethanol preserved mass (after four months of preservation, PM), and both fresh mass (FM) and dry mass (DM) for each species, using model II regressions with standardized major axis (SMA) in the R package smatr version 3.4-8 (
We used ordinary least squares (OLS) regressions in R base (
We further explored scaling relationships between FL and both FM and DM using model II regressions SMA including only an intercept term (i.e., not forced through the origin), as the femur length of adult insects does not change in response to changes in body mass (
The best-fitted models (both allometric and LMMs) were selected using Akaike’s information criterion corrected for sample size (AICc) and Akaike weight (wi) using the R package AICcmodavg version 2.3-1 (
Testing model accuracy.—We predicted fresh and dry body mass for 368 grasshopper specimens using mass-to-mass ratios, scaling regressions, and parameters from the best-fitted LMMs. We then tested the relationship between measured and predicted values using model II regressions with a major axis approach using the R package lmodel2 version 1.7-3 (
We found high measurement consistency (R > 0.970), although the degree of repeatability differed among body size proxies, species, and sexes, reflecting the relative size of the values (Suppl. material
There were strong and significant relationships between preserved mass (PM) and both fresh mass (FM, R2 ≥ 0.997, p < 0.001) and dry mass (DM, R2 ≥ 0.913, p < 0.001) in all species (Fig.
Mass-to-mass ratios for predicting both fresh and dry mass from preserved mass in three flightless New Zealand grasshopper species. Regression parameters based on standardized major axis regressions and their confidence intervals (95% CI) are shown.
Species | SMA | Intercept(CI) | Slope(CI) | R2 | p-value | Ratio |
---|---|---|---|---|---|---|
(a) Preserved mass to fresh mass (PM:FM) | ||||||
Brachaspis nivalis | 0-intercept | 0.000 | 1.045(1.041, 1.050) | 0.999 | < 0.001 | FM=1.045PM |
Brachaspis nivalis | intercept | 0.009(0.004, 0.013) | 1.030(1.021, 1.039) | 0.997 | < 0.001 | FM=1.030PM |
Paprides nitidus | 0-intercept | 0.000 | 1.045(1.041, 1.049) | 0.999 | < 0.001 | FM=1.045PM |
Paprides nitidus | intercept | 0.000(-0.003, 0.003) | 1.045(1.038, 1.052) | 0.998 | < 0.001 | FM=1.045PM |
Sigaus australis | 0-intercept | 0.000 | 1.042(1.038, 1.045) | 0.999 | < 0.001 | FM=1.042PM |
Sigaus australis | intercept | 0.002(-0.001, 0.006) | 1.039(1.033, 1.045) | 0.998 | < 0.001 | FM=1.039PM |
(b) Preserved mass to dry mass (PM:DM) | ||||||
Brachaspis nivalis | 0-intercept | 0.000 | 0.296 (0.286, 0.306) | 0.986 | < 0.001 | DM=0.296PM |
Brachaspis nivalis | intercept | -0.004 (-0.014, 0.005) | 0.308 (0.289, 0.330) | 0.913 | < 0.001 | DM=0.308PM |
Paprides nitidus | 0-intercept | 0.000 | 0.316 (0.308, 0.323) | 0.993 | < 0.001 | DM=0.316PM |
Paprides nitidus | intercept | 0.001 (-0.004, 0.006) | 0.310 (0.297, 0.324) | 0.969 | < 0.001 | DM=0.310PM |
Sigaus australis | 0-intercept | 0.000 | 0.308 (0.298, 0.319) | 0.987 | < 0.001 | DM=0.308PM |
Sigaus australis | intercept | -0.009 (-0.019, 0.001) | 0.321 (0.304, 0.338) | 0.959 | < 0.001 | DM=0.321PM |
Model selection showing the best-fitted models (AICc in bold) for predicting both fresh mass and dry mass from preserved mass in three New Zealand flightless grasshopper species. Abbreviations: K = number of parameters, AICc = Akaike’s information criterion corrected for sample size, wi = Akaike weight, LL = Log-Likelihood, R2 = marginal R2. Model parameters of the best-fitting models (ΔAICc < 2) used for predictions are shown in Suppl. material
Species | Model formulae | K | AICc | ΔAICc | wi | LL | R2 |
---|---|---|---|---|---|---|---|
(a) fresh mass (FM) as a function of preserved mass (PM) | |||||||
Brachaspis nivalis | FM~PM+Sex+(1|Site) | 5 | -808.58 | 0.00 | 0.66 | 409.53 | 0.997 |
FM~PM+Sex+(PM|Site) | 7 | -807.01 | 1.57 | 0.23 | 410.96 | 0.997 | |
FM~PM*Sex+(1|Site) | 6 | -806.38 | 2.20 | 0.22 | 409.53 | 0.997 | |
FM~PM+(1|Site) | 4 | -805.11 | 3.47 | 0.12 | 406.71 | 0.996 | |
FM~1+(1|Site) | 3 | -64.11 | 744.47 | 0.00 | 35.15 | 0.112 | |
Paprides nitidus | FM~PM+(1|Site) | 4 | -937.02 | 0.00 | 0.67 | 472.65 | 0.998 |
FM~PM+Sex+(1|Site) | 5 | -934.87 | 2.14 | 0.23 | 472.65 | 0.998 | |
FM~PM*Sex+(1|Site) | 6 | -933.26 | 3.75 | 0.10 | 472.93 | 0.998 | |
FM~PM+Sex+(PM|Site) | 7 | -931.53 | 5.49 | 0.04 | 473.17 | 0.998 | |
FM~1+(1|Site) | 3 | -35.70 | 901.31 | 0.00 | 20.94 | 0.000 | |
Sigaus australis | FM~PM+(1|Site) | 4 | -566.34 | 0.00 | 0.50 | 288.35 | 0.999 |
FM~PM+Sex+(1|Site) | 5 | -565.69 | 0.65 | 0.36 | 287.41 | 0.999 | |
FM~PM*Sex+(1|Site) | 6 | -563.69 | 2.65 | 0.13 | 288.20 | 0.999 | |
FM~PM+Sex+(PM|Site) | 7 | -561.04 | 5.31 | 0.03 | 288.20 | 0.999 | |
FM~1+(1|Site) | 3 | 69.40 | 635.75 | 0.00 | -31.56 | 0.000 | |
(b) dry mass (DM) as a function of preserved mass (PM) | |||||||
Brachaspis nivalis | DM~PM+(1|Site) | 4 | -259.16 | 0.00 | 0.73 | 134.03 | 0.915 |
DM~PM+Sex+(1|Site) | 5 | -256.70 | 2.47 | 0.21 | 134.03 | 0.915 | |
DM~PM*Sex+(1|Site) | 6 | -254.14 | 5.02 | 0.06 | 134.05 | 0.915 | |
DM~PM+Sex+(PM|Site) | 7 | -251.39 | 7.77 | 0.01 | 134.03 | 0.915 | |
DM~1+(1|Site) | 3 | -139.34 | 119.82 | 0.00 | 72.93 | 0.000 | |
Paprides nitidus | DM~PM+Sex+(PM|Site) | 7 | -300.56 | 0.00 | 0.67 | 158.65 | 0.981 |
DM~PM+Sex+(1|Site) | 5 | -298.31 | 2.25 | 0.22 | 154.85 | 0.976 | |
DM~PM*Sex+(1|Site) | 6 | -296.03 | 4.53 | 0.07 | 155.02 | 0.976 | |
DM~PM+(1|Site) | 4 | -294.75 | 5.81 | 0.04 | 151.83 | 0.972 | |
DM~1+(1|Site) | 3 | -125.73 | 174.83 | 0.00 | 66.13 | 0.000 | |
Sigaus australis | DM~PM+Sex+(PM|Site) | 7 | -258.46 | 0.00 | 0.59 | 137.53 | 0.979 |
DM~PM+Sex+(1|Site) | 5 | -257.21 | 1.25 | 0.31 | 134.27 | 0.974 | |
DM~PM*Sex+(1|Site) | 6 | -254.85 | 3.62 | 0.10 | 134.38 | 0.974 | |
DM~PM+(1|Site) | 4 | -241.01 | 17.46 | 0.00 | 124.94 | 0.964 | |
DM~1+(1|Site) | 3 | -78.24 | 180.22 | 0.00 | 42.38 | 0.000 |
Mass-to-mass relationships in three flightless New Zealand grasshopper species showing the influence of elevation and sexual dimorphism. Fresh mass–preserved mass (A–C) and dry mass–preserved mass (D–F). Sample sites (BR1 to BR5) indicating five sites in ~100-m elevation intervals from 1,383 to 1,817 m asl. Lines represent the best-fit from standardized major axis regressions. Credible intervals are omitted for clarity. Some regression lines overlie each other.
As expected, there was a strong and significant correlation (Pearson’s R ≤ 0.893, p < 0.001) among all body size measures, with pairwise comparisons involving femur length (FL) having the highest correlation coefficients (Pearson’s R > 0.924, p < 0.001; Suppl. material
Length–mass scaling coefficients for predicting both fresh and dry mass from femur length in three flightless New Zealand grasshopper species. Regression parameters based on standardized major axis regressions and their confidence intervals (95% CI) are shown.
Species | Model formulae | Intercept(CI) | Slope(CI) | R2 | p-value |
---|---|---|---|---|---|
(a) fresh mass (FM) as a function of femur length (FL) | |||||
Brachaspis nivalis | ln(FM)~ln(FL) | -7.754(-7.937, -7.571) | 2.696(2.625, 2.768) | 0.965 | < 0.001 |
Paprides nitidus | ln(FM)~ln(FL) | -8.914(-9.085, -8.743) | 3.090(3.024, 3.157) | 0.976 | < 0.001 |
Sigaus australis | ln(FM)~ln(FL) | -9.584(-9.783, -9.385) | 3.315(3.241, 3.391) | 0.982 | < 0.001 |
(b) dry mass (DM) as a function of femur length (FL) | |||||
Brachaspis nivalis | ln(DM)~ln(FL) | -9.234 (-9.747, -8.721) | 2.778(2.585, 2.986) | 0.898 | < 0.001 |
Paprides nitidus | ln(DM)~ln(FL) | -10.077(-10.504, -9.650) | 3.071(2.908, 3.242) | 0.953 | < 0.001 |
Sigaus australis | ln(DM)~ln(FL) | -11.423(-11.919, -10.927) | 3.539(3.357, 3.731) | 0.939 | < 0.001 |
Model selection showing the best-fitted models (AICc in bold) for predicting both fresh mass and dry mass from femur length in three flightless New Zealand grasshopper species. Abbreviations: K = number of parameters, AICc = Akaike’s information criterion corrected for sample size, wi = Akaike weight, LL = Log-Likelihood, R2 = marginal R2. Model parameters of the best-fitting models (ΔAICc < 2) used for predictions are shown in Suppl. material
Species | Model formulae | K | AICc | ΔAICc | wi | LL | R2 |
---|---|---|---|---|---|---|---|
(a) fresh mass (FM) as a function of femur length (FL) | |||||||
Brachaspis nivalis | ln(FM)~ln(FL)*Sex+(1|Site) | 6 | -284.34 | 0.00 | 0.44 | 148.51 | 0.968 |
ln(FM)~ln(FL)+Sex+(ln(FL)|Site) | 7 | -283.44 | 0.90 | 0.28 | 149.18 | 0.969 | |
ln(FM)~ln(FL)+Sex+(1|Site) | 5 | -283.22 | 1.12 | 0.25 | 146.85 | 0.967 | |
ln(FM)~ln(FL)+(1|Site) | 4 | -278.56 | 5.78 | 0.02 | 143.44 | 0.965 | |
ln(FM)~1+(1|Site) | 3 | 149.94 | 434.28 | 0.00 | -71.88 | 0.111 | |
Paprides nitidus | ln(FM)~ln(FL)+(1|Site) | 4 | -328.73 | 0.00 | 0.64 | 169.58 | 0.976 |
ln(FM)~ln(FL)+Sex+(1|Site) | 5 | -327.15 | 1.58 | 0.29 | 169.88 | 0.981 | |
ln(FM)~ln(FL)*Sex+(1|Site) | 6 | -324.43 | 4.30 | 0.07 | 169.62 | 0.981 | |
ln(FM)~ln(FL)+Sex+(ln(FL)|Site) | 7 | -296.49 | 32.24 | 0.00 | 152.38 | 0.981 | |
ln(FM)~1+(1|Site) | 3 | 247.53 | 576.26 | 0.00 | -120.68 | 0.000 | |
Sigaus australis | ln(FM)~ln(FL)+Sex+(1|Site) | 5 | -180.21 | 0.00 | 0.65 | 95.46 | 0.987 |
ln(FM)~ln(FL)+(1|Site) | 4 | -178.53 | 1.68 | 0.28 | 95.77 | 0.982 | |
ln(FM)~ln(FL)*Sex+(1|Site) | 6 | -175.85 | 4.36 | 0.07 | 95.61 | 0.987 | |
ln(FM)~ln(FL)+Sex+(ln(FL)|Site) | 7 | -156.20 | 24.01 | 0.00 | 82.34 | 0.987 | |
ln(FM)~1+(1|Site) | 3 | 204.43 | 384.63 | 0.00 | -99.07 | 0.000 | |
(b) dry mass (DM) as a function of femur length (FL) | |||||||
Brachaspis nivalis | ln(DM)~ln(FL)+(1|Site) | 4 | -45.22 | 0.00 | 0.48 | 27.05 | 0.904 |
ln(DM)~ln(FL)+Sex+(1|Site) | 5 | -44.42 | 0.80 | 0.32 | 27.89 | 0.902 | |
ln(DM)~ln(FL)*Sex+(1|Site) | 6 | -43.14 | 2.08 | 0.17 | 28.55 | 0.904 | |
ln(DM)~ln(FL)+Sex+(FL|Site) | 7 | -39.14 | 6.08 | 0.02 | 27.90 | 0.903 | |
ln(DM)~1+(1|Site) | 3 | 66.45 | 111.67 | 0.00 | -29.96 | 0.000 | |
Paprides nitidus | ln(DM)~ln(FL)+Sex+(1|Site) | 5 | -69.02 | 0.00 | 0.53 | 40.21 | 0.962 |
ln(DM)~ln(FL)*Sex+(1|Site) | 6 | -68.45 | 0.57 | 0.40 | 41.23 | 0.964 | |
ln(DM)~ln(FL)+(1|Site) | 4 | -67.97 | 1.05 | 0.03 | 35.94 | 0.955 | |
ln(DM)~ln(FL)+Sex+(ln(FL)|Site) | 7 | -63.98 | 5.04 | 0.04 | 40.13 | 0.963 | |
ln(DM)~1+(1|Site) | 3 | 85.46 | 154.48 | 0.00 | -39.46 | 0.000 | |
Sigaus australis | ln(DM)~ln(FL)+(1|Site) | 4 | -28.96 | 0.00 | 0.65 | 18.93 | 0.955 |
ln(DM)~ln(FL)+Sex+(1|Site) | 5 | -26.75 | 2.21 | 0.21 | 19.06 | 0.955 | |
ln(DM)~ln(FL)+Sex+(ln(FL)|Site) | 7 | -24.78 | 4.19 | 0.08 | 20.72 | 0.960 | |
ln(DM)~ln(FL)*Sex+(1|Site) | 6 | -24.27 | 4.70 | 0.06 | 19.11 | 0.956 | |
ln(DM)~1+(1|Site) | 3 | 120.31 | 149.28 | 0.00 | -56.90 | 0.000 |
Length-to-mass relationships in three flightless New Zealand grasshopper species showing the influence of elevation and sexual dimorphism. Fresh mass–femur length (A–C) and dry mass–femur length (D–F). Length–mass relationships are shown on natural logarithmic axes (ln). Sample sites (BR1 to BR5) indicating five sites in ~100-m elevation intervals from 1,383 to 1,817 m asl. Lines represent the best-fit from standardized major axis regressions. Credible intervals are omitted for clarity. Some regression lines overlie each other.
We found that predicted body mass (both fresh and dry mass) was significantly correlated with empirical measurements; however, using PM as a predictor led to the most accurate estimates (Fig.
Details of statistical models (type II linear regression with a major axis) testing the relationships between predicted and measured body mass in three flightless New Zealand grasshopper species. Predictions are based on mass-to-mass ratios and scaling parameters from standardized major axis regressions (SMA) and linear mixed-effects models (LMM). The R2 values, estimated intercept, and slope (95% confidence intervals) are given.
Model | Sample size | R2 | Intercept(CI) | Slope(CI) | p-value |
---|---|---|---|---|---|
(a) Preserved mass to fresh mass | |||||
PM:FM ratio | 368 | 0.998 | 0.004(0.002–0.006) | 0.993 (0.989–0.998) | < 0.001 |
LMM | 368 | 0.998 | -0.004(-0.006–-0.002) | 1.005 (1.004–1.010) | < 0.001 |
(b) Preserved mass to dry mass | |||||
PM:DM ratio | 150 | 0.957 | -0.006(-0.011–0.001) | 1.035 (1.000–1.071) | < 0.001 |
LMM | 150 | 0.958 | -0.004(-0.009–0.001) | 1.032 (0.997–1.068) | < 0.001 |
(c) femur length to fresh mass | |||||
SMA | 368 | 0.965 | -0.006 (-0.021–0.009) | 1.013 (0.982–1.045) | < 0.001 |
LMM | 368 | 0.963 | -0.031 (-0.048–-0.016) | 1.056 (1.023–1.091) | < 0.001 |
(d) femur length to dry mass | |||||
SMA | 150 | 0.898 | -0.004(-0.013–0.002) | 1.034 (0.979–1.092) | < 0.001 |
LMM | 150 | 0.901 | -0.009(-0.018–0.002) | 1.088 (1.031–1.148) | < 0.001 |
High predictability observed when comparing measured and predicted body mass using type-II linear regression with a major axis approach. Predictions based on preserved mass (A–D) and femur length (E–H) pooling data from three flightless New Zealand grasshopper species: Brachaspis nivalis (pink circles), Paprides nitidus (green triangles), and Sigaus australis (blue squares). The expected x = y relationship is shown in dashed black line, and the observed is shown in solid grey line. Predictions from standardized major axis regressions (SMA) and linear mixed-effects models (LMM) are shown. Note that in most cases fitting lines overlap.
A key source of variation in morphological traits is measurement repeatability, which is inherently related to the statistical power of analyses based on those measurements (
Collecting and storing insects in chemical fluids, such as ethanol, has the potential to alter their body mass (
Studies of the mass-to-mass relationships of terrestrial insects are scarce (e.g.,
The choice of a robust linear size trait is an important consideration for accurate mass estimates when applying allometric scaling regressions (
As expected, sex was sometimes retained as an informative predictor of body mass when used in addition to or as an interaction with femur length. This is not surprising given that adult females of these grasshopper species are approximately three times as heavy as adult males. Including sex generally increased model fit (Tables
The difficulty of accurately predicting intraspecific body size variation based on co-varying linear traits is not new. The lack of predictive power has previously been explained in terms of traits varying in response to environmental conditions during development (
The slope parameter β (power coefficient) of our femur length regressions ranged between 2.152 and 3.293 for fresh mass and between 2.544 and 3.425 for dry mass, thus being close to 3 as expected for animals with isometric growth (
One source of potential error in our models is intraspecific regional variation in body size. This limitation can be problematic because scaling relationships in terrestrial insects, and thus, their regression parameters, are likely to vary geographically if populations’ body size evolve independently of one another depending on local conditions (e.g.,
Ecological applications.—Here we show that, for New Zealand grasshoppers, two easy-to-measure, non-destructive, and highly repeatable size estimates (i.e., preserved mass and femur length) are good predictors of other difficult-to-measure but ecologically meaningful size traits, such as fresh and dry mass. Many ecological disciplines typically require body mass data to relate body size to a range of ecological attributes. For example, body mass has been proposed as a suitable metric for testing ecogeographic patterns, such as Bergmann’s rule (
Body mass estimates from scaling regressions have proven useful for studying aspects shaping arthropod communities including biomass production (e.g.,
Recently, declines in body size have been proposed as a general response to anthropogenic climate change in both endothermic and ectothermic animals (
The authors thank Broken River Ski Area and its manager, Dr Claire Newell, who allowed us access to the field site, and the New Zealand Department of Conservation for granting collecting permits (Authorization Number: 49878-RES and 97397-FLO). We also acknowledge our field partners: Mari Nakano, Evans Effah, and Andrea Clavijo. This research was supported by a grant from the Orthopterists’ Society’s Theodore J. Cohn Research Fund and a doctoral scholarship from Massey University (awarded to FLMJ). The manuscript was improved by constructive feedback from Derek Woller and Maria Celeste Scattolini.
Data type: docx file
Explanation note: Appendix 1. Measurement repeatability based on repeated measures of body size traits from the same specimens in three New Zealand grasshopper species. Appendix 2. Effect of the preservation method (i.e., 95% ethanol) on body mass by comparing mass estimates between live (fresh mass) and preserved states (preserved mass after two and four months of preservation) in three New Zealand grasshopper species. Appendix 3. Intraspecific relationships between preserved mass and both fresh and dry mass in three New Zealand grasshopper species. Appendix 4. Regression parameters for the best-fitted linear mixed-effect models for body mass prediction based on preserved mass (Table