DOI: 10.5061/dryad.cc2fqz6kp
title: Trade-offs between brain and digestive tissues across elevations in<em>Typhlomys daloushanensis</em> : evidence for sexual dimorphism

description: To cope with highly stochastic and/or heterogeneous environmental
 conditions, animals must balance energy resource allocation across
 physiological processes. The digestive tract and brain exhibit structural
 variations under strong developmental and selective pressures that vary
 across environmental gradients both between and within species. Here, we
 measured body mass, body length, digestive tract segments lengths
 (stomach, cecum, small intestine, large intestine), brain weight, and
 relative brain size (scale mass index, SMI residuals) for 67 Chinese pygmy
 dormice (Typhlomys daloushanensis, 29 females and 38 males), an ancient,
 small, arboreal rodent species with echolocation abilities, captured at 37
 sites between 414 and 1757 m. From Standardized Major Axis (SMA)
 regressions, we found no significant relationship between body size (SMI)
 and elevation. Notably, neither digestive tract segment lengths and their
 residuals nor brain weight (absolute and residual) correlated
 significantly with elevation in either sex, and slopes did not differ
 between males and females, providing no support for the Digestive Tract
 Theory (DTT) or the Cognitive Buffer Hypothesis (CBH). However,
 brain–digestive tract relationships exhibited sex-specific differences,
 partially supporting the Expensive Tissue Hypothesis (ETH), suggesting
 that energy allocation to high-cost organs is sex-dependent. Males
 maintained relatively heavier brain weight under comparable digestive
 tract lengths, likely to meet cognitive demands associated with mate
 competition, territorial defense, and exploratory behavior, whereas
 females tended to prioritize digestive tract investment to meet the
 energetic demands of gestation and lactation. Thus, classical predictions
 of body size–environment relationships may be overridden by sex-specific
 physiological trade-offs in specialized species, providing new insights
 into how small mammals may adapt to rapid environmental change.
description: # Trade-offs between brain and digestive tissues across elevations
 in*Typhlomys daloushanensis* : evidence for sexual dimorphism Dataset DOI:
 [10.5061/dryad.cc2fqz6kp](https://doi.org/10.5061/dryad.cc2fqz6kp) ##
 Description of the data and file structure The "data.xlsx"
 comprises measurements of physiological and morphological characteristics
 of *Typhlomys daloushanensis*. The dataset includes 67 samples, with 29
 females and 38 males. The primary objective of this dataset is to
 investigate the impact of environmental gradients on the physiological
 traits of animals, particularly the structural variations in the brain and
 digestive organs. The accompanying R script performs comprehensive data
 analysis on this dataset. It includes data cleaning, transformation
 (logarithmic transformation and residual calculation), and statistical
 modeling using Standardized Major Axis (SMA) regression to explore
 relationships between body traits and elevation. The script also generates
 visualizations to illustrate these relationships and their differences
 between sexes. The analysis aims to provide insights into how
 environmental gradients influence the physiological traits of Typhlomys
 daloushanensis. ### Files and variables #### File: data.xlsx
 **Description:** This dataset comprises measurements of the physiological
 and morphological characteristics of Typhlomys daloushanensis. The dataset
 includes 67 samples, with 29 females and 38 males. Data were collected
 from 37 sites across different elevations, ranging from 414 to 1757
 meters.The primary objective of this dataset is to investigate the impact
 of environmental gradients on the physiological traits of animals,
 particularly the structural variations in the brain and digestive organs.
 ##### Variables * mouse_number: The unique identification number for each
 mouse, used to distinguish different samples. * Weight: The weight of the
 mouse, measured in grams (g). This is an important indicator of the
 mouse's body size. * SVL: Measured in centimeters (cm). SVL is a
 commonly used indicator of the mouse's body length and is often
 employed in ecological and morphological studies. *
 Total_Intestine_Length: The length of the total intestine, measured in
 centimeters (cm) * Stomach_Length: The length of the stomach, measured in
 centimeters (cm).   * Small_intestine_Length: The length of the small
 intestine, measured in centimeters (cm). As an important part of the
 digestive system, the length of the small intestine can reflect the
 mouse's digestive and absorption capabilities. * Caecum_Length: The
 length of the cecum, measured in centimeters (cm). *
 Large_intestine_Length: The length of the large intestine, measured in
 centimeters (cm). * elevation: The elevation of the sampling site,
 measured in meters (m). Elevation is an important variable for studying
 the impact of environmental gradients on the physiological characteristics
 of animals. * sex: The sex of the mouse, categorized as "Male"
 or "Female." Sex is an important variable for studying the
 impact of gender differences on physiological characteristics. *
 brain_fresh: The fresh weight of the brain, measured in grams (g). This
 direct indicator of the mouse's brain size helps to study the
 relationship between the brain and other body organs. * SMI: The Scale
 Mass Index (SMI) is a standardized indicator used to adjust the
 relationship between brain weight and body weight, thereby more accurately
 reflecting the relative size of the brain. #### File: code.R
 **Description:** This R script performs comprehensive data analysis on
 physiological and morphological measurements of Typhlomys daloushanensis,
 including data cleaning, transformation, and statistical modeling using
 SMA (Standardized Major Axis) regression to explore relationships between
 body traits and elevation. The script also generates visualizations to
 illustrate these relationships and their differences between sexes.