page_title: Phenotypic integration
section_title: Natural Selection and Phenotypic Integration
hierarchical_section_title: Phenotypic integration / Natural Selection and Phenotypic Integration
caption_attribution_description: English: Thamnophis ordinoides. We saw this snake at the Mount Townsend trail head, on the Olympic Peninsula, Washington, USA.
context_page_description: Phenotypic Integration occurs when multiple functionally-related traits are correlated with each other. Complex phenotypes often require multiple traits working together in order to function properly. Phenotypic integration is significant because it provides an explanation as to how phenotypes are sustained by relationships between traits. Every organism's phenotype is integrated, organized, and a functional whole. Integration is also associated with functional modules. Modules are complex character units that are tightly associated, such as a flower. It is hypothesized that organisms with high correlations between traits in a module have the most efficient functions. The fitness of a particular value for one phenotypic trait frequently depends on the value of the other phenotypic traits, making it important for those traits evolve together. One trait can have a direct effect on fitness, and it has been shown that the correlations among traits can also change fitness, causing these correlations to be adaptive, rather than solely genetic. Integration can be involved in multiple aspects of life, not just at the genetic level, but during development, or simply at a functional level.
context_section_description: Phenotypic Integration can be favorable or unfavorable with respect to natural selection. It has been shown that certain combinations of correlated traits can be unfavorable to an organism.  In an ontogenetic study of laboratory rats, certain covariances among developmental characters which produced differing functions in the skull and limb were less favorable than another set that contributed to skull and limb structure. The most common form of selection on phenotypic integration is correlational selection.  Correlational selection is a form of natural selection that favors certain combinations of traits (phenotypic integration). It can promote both genetic correlations and high levels of genetic variation. It has even been found that correlational selection may be the most common form of natural selection. Occasionally, this form of selection will favor a group of traits at the expense of others and if it does favor a particular set of traits it will include the most used traits whose functional effectiveness is essential for their ability to work together, and whose successful interaction is needed for the fitness of the individual. Phenotypic integration may be the adaptive product of correlational selection. An example of natural selection favoring integration is in the color patterns and escape mechanisms of the Garter snake, Thamnophis Ordinoides. Another example is in plants that have highly-specific pollinators, natural selection favors plants that have highly specialized flowering to pair with the specific pollinators, and therefore high floral integration.
caption: Northwestern Garter Snake's color patterns and escape mechanisms are integrated.
exif: {"Image Make": "Canon", "Image Model": "Canon PowerShot SD850 IS", "Image Orientation": "Horizontal (normal)", "Image DateTime": "2010:07:10 09:15:12", "Image YCbCrPositioning": "Centered", "Image Tag 0x1001": "3264", "Image Tag 0x1002": "2448", "Image ExifOffset": "2246", "Image Padding": "[]", "Image OffsetSchema": "4150", "EXIF ExposureTime": "1/500", "EXIF FNumber": "14/5", "EXIF ISOSpeedRatings": "250", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2010:07:10 09:15:12", "EXIF DateTimeDigitized": "2010:07:10 09:15:12", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "5", "EXIF ShutterSpeedValue": "287/32", "EXIF ApertureValue": "95/32", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "95/32", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, auto mode", "EXIF FocalLength": "29/5", "EXIF SubSecTimeOriginal": "00", "EXIF SubSecTimeDigitized": "00", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3264", "EXIF ExifImageLength": "2448", "EXIF FocalPlaneXResolution": "43520/3", "EXIF FocalPlaneYResolution": "2448000/169", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard", "EXIF Padding": "[]", "EXIF OffsetSchema": "2120"}